All answers should be in radians not degrees. 1) (15 pts total) Conditional Probability Two integrated circuits made from the same wafer are tested. Each IC either passes the test or fails the test. The event that the first IC fails the test is called A. The event that the second IC fails the test is called B. The probability of A, P(A)=0.02. The probability of B, P(B)=0.02. The probability that both ICs fail is ?(?∩?)?? 0.01. What is the conditional probability P(B|A) the the 2nd IC fails the test given that the first IC failed the test? 2) (20 points total) Sampling with replacement The NAU student ID number is a 7-digit number. Assume all numbers are randomly generated, and all numbers are equally likely to be generated. a) (5 ???) How many possible student ID numbers are there? b) (5 ???) What is the probability of getting the ID number that is all 1s, 1111111? c) (5 ???) How many student ID numbers have a 1 as the first digit? d) (5 ???) What is the probability of getting a student ID number with a 1 as the first digit? 3) (15 pts total) Sampling without replacement A box in the EE188 lab contains 200 resistors that are labeled 100kΩ resistors. Five of these resistors are in fact 10 kΩ resistors (only 5!) Your circuit design uses 3 100 kΩ resistors. a) (5 pts) What is the probability that all 3 of the resistors you choose are 100kΩ resistors? b) (5 pts) What is the probability that one or more or the 3 resistors that you chose aren’t 100 kΩ resistors? Hint: use the answer from part a) c) (5 pts) What is the probability that all 3 resistors that you chose are not 100 kΩ resistors. 4) (20 pts total) Combinations: Arrangements where order doesn’t matter a) (3 pts) How many ways are there to draw 3 resistors from a box of 200 resistors? b) (3 pts) How many ways are there to draw 3 resistors from a group of 195 100 kΩ resistors? c) (4 pts) Calculate the probability of drawing 3 100 kΩ resistors from a box of 200 resistors, where 195 are 100 kΩ resistors and 5 are 10 kΩ resistors. Use your results from a) and b) to find this probability. d) (2 pts) Is your answer in c) the same as 3a)? e) (3 pts) How many ways are there to draw 3 resistors from a group of 5 10 kΩ resistors? f) (3 pts) Calculate the probability of drawing 3 10 kΩ resistors from a box of 200 resistors, where 195 are 100 kΩ resistors and 5 are 10 kΩ resistors. Use your results from a) and e) to find this probability. g) (2 pts) Is your answer in f) the same as your answer from 3c)? 5) (20 pts) For the following data set: 70.6, 70.9, 69.1, 71.3, 70.5, 69.7, 71.5, 69.8, 71.1, 68.9, 70.3, 69.2, 71.2, 70.4, 72.8 a) (5 pts) Draw a histogram with bin size 0.5, starting at the bin 68.45-68.95 b) (5 pts) What is the mean of the data? c) (5 pts) What is the median of the data? d) (5 pts) What is the standard deviation of the data?

All answers should be in radians not degrees. 1) (15 pts total) Conditional Probability Two integrated circuits made from the same wafer are tested. Each IC either passes the test or fails the test. The event that the first IC fails the test is called A. The event that the second IC fails the test is called B. The probability of A, P(A)=0.02. The probability of B, P(B)=0.02. The probability that both ICs fail is ?(?∩?)?? 0.01. What is the conditional probability P(B|A) the the 2nd IC fails the test given that the first IC failed the test? 2) (20 points total) Sampling with replacement The NAU student ID number is a 7-digit number. Assume all numbers are randomly generated, and all numbers are equally likely to be generated. a) (5 ???) How many possible student ID numbers are there? b) (5 ???) What is the probability of getting the ID number that is all 1s, 1111111? c) (5 ???) How many student ID numbers have a 1 as the first digit? d) (5 ???) What is the probability of getting a student ID number with a 1 as the first digit? 3) (15 pts total) Sampling without replacement A box in the EE188 lab contains 200 resistors that are labeled 100kΩ resistors. Five of these resistors are in fact 10 kΩ resistors (only 5!) Your circuit design uses 3 100 kΩ resistors. a) (5 pts) What is the probability that all 3 of the resistors you choose are 100kΩ resistors? b) (5 pts) What is the probability that one or more or the 3 resistors that you chose aren’t 100 kΩ resistors? Hint: use the answer from part a) c) (5 pts) What is the probability that all 3 resistors that you chose are not 100 kΩ resistors. 4) (20 pts total) Combinations: Arrangements where order doesn’t matter a) (3 pts) How many ways are there to draw 3 resistors from a box of 200 resistors? b) (3 pts) How many ways are there to draw 3 resistors from a group of 195 100 kΩ resistors? c) (4 pts) Calculate the probability of drawing 3 100 kΩ resistors from a box of 200 resistors, where 195 are 100 kΩ resistors and 5 are 10 kΩ resistors. Use your results from a) and b) to find this probability. d) (2 pts) Is your answer in c) the same as 3a)? e) (3 pts) How many ways are there to draw 3 resistors from a group of 5 10 kΩ resistors? f) (3 pts) Calculate the probability of drawing 3 10 kΩ resistors from a box of 200 resistors, where 195 are 100 kΩ resistors and 5 are 10 kΩ resistors. Use your results from a) and e) to find this probability. g) (2 pts) Is your answer in f) the same as your answer from 3c)? 5) (20 pts) For the following data set: 70.6, 70.9, 69.1, 71.3, 70.5, 69.7, 71.5, 69.8, 71.1, 68.9, 70.3, 69.2, 71.2, 70.4, 72.8 a) (5 pts) Draw a histogram with bin size 0.5, starting at the bin 68.45-68.95 b) (5 pts) What is the mean of the data? c) (5 pts) What is the median of the data? d) (5 pts) What is the standard deviation of the data?

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Chapter 03 Homework Due: 11:59pm on Friday, May 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Components and Structure of the Atom Learning Goal: To specify the basic components of the atom and describe our modern conception of its structure. Part A The atom consists of three types of subatomic particles: protons, neutrons, and electrons. The electron is by far the lightest of the three, while the much heavier proton and neutron have masses very similar to each other. Two of the types of particles carry an electrical charge, while the third is neutral. Label the subatomic particles and appropriate charges by their relative locations. Identify the subatomic particles by dragging the appropriate labels to their respective targets. Hint 1. Which subatomic particles carry electric charge? Of the three subatomic particles, two carry equal but opposite charges. Select the two correct statements that match the subatomic particle with the appropriate charge. Check all that apply. ANSWER: Hint 2. Which subatomic particles are not found in the nucleus? Protons and electrons carry equal but opposite charges. Atomic nuclei are positively charged and are not composed of negatively charged particles. Which types of subatomic particles cannot be located within the nucleus? Select any that apply. ANSWER: ANSWER: The electron carries a positive charge. The proton carries a positive charge. The neutron carries a positive charge. The proton carries a negative charge. The electron carries a negative charge. The neutron carries a negative charge. neutrons electrons protons Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 1 of 14 5/21/2014 8:02 PM Correct This image represents the classical model of the atom proposed by Niels Bohr. Although this model has changed slightly as the result of modern scientific discoveries, it does help in understanding the relative locations of the subatomic particles in the atom. Notice that the protons and neutrons are bound in the nucleus, while the electrons are located in the space surrounding the nucleus. Part B Of the three types of subatomic particles, only neutrons do not carry charge. Protons carry a positive charge, and electrons carry a negative charge. Protons and neutrons are bound in the nucleus, while electrons orbit the nucleus. When the number of each type of subatomic particle in an atom changes, the characteristics defining the atom also change. Match the appropriate phrases with the type of subatomic particle that completes the defining characteristic. Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. Hint 1. What type of subatomic particle is lost or gained when an ion forms? For any atom of a given element to go from being neutral ( ) to being ionized ( ), what type of subatomic particle must be lost or gained? Select all that apply. ANSWER: Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 2 of 14 5/21/2014 8:02 PM Hint 2. What type of subatomic particle identifies an element? When identifying the element classification of a particular atom, which type of subatomic particle is used? ANSWER: ANSWER: Correct The number of each type of subatomic particle plays an important role in the characteristics of the atom. The general element classification (hydrogen, carbon, oxygen, etc.) is governed by the number of protons in the nucleus. If the number of protons changes in an atom, so does the type of element. The electrons are the only type of subatomic particle not in the nucleus. They orbit around the nucleus, bound by the electromagnetic force. When electrons are lost or gained by a neutral atom, the charge balance shifts, resulting in the atom becoming an ion. Ions can be either positive when electrons are lost or negative when electrons are gained. Part C In the classical view of the atom, Bohr pictured electrons orbiting the positively charged nucleus similar to how the planets orbit the Sun. While this picture was not entirely correct, it provides a good framework in which to make calculations about the energies of electrons. Different from the predictions of Newtonian mechanics, which allows any energy to be possible, Bohr described the electron orbits (now called orbitals) as having specific energies. Rank the following electron energy states according to their electron energies. Rank from highest to lowest energies. Hint 1. What are the definitions of orbital, ground state, and excited state? Define orbital, ground state, and excited state. loss of an electron loss of a proton loss of a neutron gain of an electron gain of a proton gain of a neutron electron proton neutron Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 3 of 14 5/21/2014 8:02 PM Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. ANSWER: Hint 2. How does the state change when an electron absorbs energy? Electrons can absorb energy either from light radiation or from collisions with other atoms. If an electron is in the first excited energy state and absorbs enough energy to go to the next higher energy state, into what state will the electron transition? ANSWER: ANSWER: the ground state the second excited state the third excited state Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 4 of 14 5/21/2014 8:02 PM Correct Excited states refer to the energy of an electron. The higher the state, the higher the energy of the electron. The electron energies of each orbital are fixed. The energy required for an electron to transition between each orbital is an exact value, corresponding to the difference between the orbital energies. Any energy more or less than these precise differences cannot be used by the electron to make a transition; only the energies equal to the full values can induce a transition. Part D The Bohr model accounted for most of the general characteristics of the atom. However, the modern model based on quantum mechanics explains that, although the energy of each orbital is fixed, the orbital radius is actually an average distance. The result is a “cloud” where the electron is most likely to be located. The following is an image of an atom of hydrogen, consisting of one proton, zero neutrons, and one electron. When an electron is excited to different energy levels, the radius from the nucleus also changes. Rank the following electron energy states according to the average distance of the electron from the nucleus. Rank from largest to smallest distances. Hint 1. What is the relationship between electron orbital distance and electron energy? Rank the following general electron energies from largest to smallest electron orbital distances. Rank from largest to smallest orbital distances. ANSWER: ANSWER: Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 5 of 14 5/21/2014 8:02 PM Correct Excited states refer to the energy state of an electron. The higher the state, the higher the energy and the greater the distance of the electron from the nucleus. Due to the attractive force between the negatively charged electron and the positively charged nucleus, the electron requires greater energies to overcome this attraction and achieve orbits at greater distances. Concept Review: The pH Scale Can you classify solutions as acidic, neutral, or basic? Part A Decide whether each label describes a solution that is acidic, neutral, or basic, and then drag it into the appropriate bin. ANSWER: Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 6 of 14 5/21/2014 8:02 PM Correct Activity: Carbohydrates Click here to complete this activity. Then answer the questions. Part A Glycogen is _____. ANSWER: Correct Animals store energy in the form of glycogen. a polysaccharide found in animals a source of saturated fat a polysaccharide found in plant cell walls the form in which plants store sugars a transport protein that carries oxygen Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 7 of 14 5/21/2014 8:02 PM Part B glucose + glucose —> _____ by _____. ANSWER: Correct Maltose is the disaccharide formed when two glucose molecules are linked by dehydration synthesis. Part C Which of these is a source of lactose? ANSWER: Correct Lactose is the sugar found in milk. Part D Which of these is a polysaccharide? ANSWER: Correct Cellulose is a carbohydrate composed of many monomers. Part E _____ is the most abundant organic compound on Earth. ANSWER: maltose + water … dehydration synthesis lactose + water … hydrolysis starch + water … dehydration synthesis sucrose + water … dehydration synthesis cellulose + water … hydrolysis potatoes sugar beets sugar cane starch milk sucrose lactose glucose galactose cellulose Cellulose Lactose Starch Glucose Glycogen Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 8 of 14 5/21/2014 8:02 PM Correct Cellulose, a component of plant cell walls, is the most abundant organic compound found on earth. Activity: Protein Structure Click here to complete this activity. Then answer the questions. Part A Proteins are polymers of _____. ANSWER: Correct Proteins are polymers of amino acids. Part B What type of bond joins the monomers in a protein’s primary structure? ANSWER: Correct The amino acids of a protein are linked by peptide bonds. Part C Which of these illustrates the secondary structure of a protein? ANSWER: nucleotides CH2O units glycerol hydrocarbons amino acids ionic hydrogen hydrophobic S—S peptide Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 9 of 14 5/21/2014 8:02 PM Correct Alpha helices and beta pleated sheets are characteristic of a protein’s secondary structure. Part D The secondary structure of a protein results from _____. ANSWER: Correct Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges. Part E Tertiary structure is NOT directly dependent on _____. ANSWER: bonds between sulfur atoms peptide bonds hydrogen bonds hydrophobic interactions ionic bonds hydrophobic interactions ionic bonds hydrogen bonds peptide bonds bonds between sulfur atoms Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 10 of 14 5/21/2014 8:02 PM Correct Peptide bonds link together the amino acids of a protein’s primary structure. Activity: Lipids Click here to complete this activity. Then answer the questions. Part A Which of these is NOT a lipid? ANSWER: Correct RNA is a nucleic acid Part B This figure is an example of a(n) _____. ANSWER: Correct The fatty acid tails lack double bonds. steroids phospholipid RNA cholesterol wax steroid unsaturated fat nucleic acid protein saturated fat Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 11 of 14 5/21/2014 8:02 PM Part C Which of these is a phospholipid? ANSWER: Correct Phospholipids are composed of a phosphate group, a glycerol, and fatty acids. Part D Which of these is rich in unsaturated fats? ANSWER: Correct Olive oil is a plant oil, and most plant oils are rich in unsaturated fats. Part E beef fat lard butter olive oil a fat that is solid at room temperature Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 12 of 14 5/21/2014 8:02 PM A function of cholesterol that does not harm health is its role _____. ANSWER: Correct Cholesterol is an important component of animal cell membranes. Concept Review: Types of Macromolecules Can you identify characteristics of proteins, nucleic acids, and carbohydrates? Part A Decide whether each label describes proteins, nucleic acids, or carbohydrates, and then drag it into the appropriate bin. ANSWER: Correct Concept Review: Earth’s Interior Layers Can you identify characteristics of Earth’s interior layers? Part A Drag the labels to the appropriate targets. ANSWER: as a component of animal cell membranes in calcium and phosphate metabolism All of cholesterol’s effects cause the body harm. as the most abundant male sex hormone as the primary female sex hormone Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 13 of 14 5/21/2014 8:02 PM Correct Score Summary: Your score on this assignment is 99.6%. You received 31.87 out of a possible total of 32 points. Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 14 of 14 5/21/2014 8:02 PM

Chapter 03 Homework Due: 11:59pm on Friday, May 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Components and Structure of the Atom Learning Goal: To specify the basic components of the atom and describe our modern conception of its structure. Part A The atom consists of three types of subatomic particles: protons, neutrons, and electrons. The electron is by far the lightest of the three, while the much heavier proton and neutron have masses very similar to each other. Two of the types of particles carry an electrical charge, while the third is neutral. Label the subatomic particles and appropriate charges by their relative locations. Identify the subatomic particles by dragging the appropriate labels to their respective targets. Hint 1. Which subatomic particles carry electric charge? Of the three subatomic particles, two carry equal but opposite charges. Select the two correct statements that match the subatomic particle with the appropriate charge. Check all that apply. ANSWER: Hint 2. Which subatomic particles are not found in the nucleus? Protons and electrons carry equal but opposite charges. Atomic nuclei are positively charged and are not composed of negatively charged particles. Which types of subatomic particles cannot be located within the nucleus? Select any that apply. ANSWER: ANSWER: The electron carries a positive charge. The proton carries a positive charge. The neutron carries a positive charge. The proton carries a negative charge. The electron carries a negative charge. The neutron carries a negative charge. neutrons electrons protons Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 1 of 14 5/21/2014 8:02 PM Correct This image represents the classical model of the atom proposed by Niels Bohr. Although this model has changed slightly as the result of modern scientific discoveries, it does help in understanding the relative locations of the subatomic particles in the atom. Notice that the protons and neutrons are bound in the nucleus, while the electrons are located in the space surrounding the nucleus. Part B Of the three types of subatomic particles, only neutrons do not carry charge. Protons carry a positive charge, and electrons carry a negative charge. Protons and neutrons are bound in the nucleus, while electrons orbit the nucleus. When the number of each type of subatomic particle in an atom changes, the characteristics defining the atom also change. Match the appropriate phrases with the type of subatomic particle that completes the defining characteristic. Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. Hint 1. What type of subatomic particle is lost or gained when an ion forms? For any atom of a given element to go from being neutral ( ) to being ionized ( ), what type of subatomic particle must be lost or gained? Select all that apply. ANSWER: Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 2 of 14 5/21/2014 8:02 PM Hint 2. What type of subatomic particle identifies an element? When identifying the element classification of a particular atom, which type of subatomic particle is used? ANSWER: ANSWER: Correct The number of each type of subatomic particle plays an important role in the characteristics of the atom. The general element classification (hydrogen, carbon, oxygen, etc.) is governed by the number of protons in the nucleus. If the number of protons changes in an atom, so does the type of element. The electrons are the only type of subatomic particle not in the nucleus. They orbit around the nucleus, bound by the electromagnetic force. When electrons are lost or gained by a neutral atom, the charge balance shifts, resulting in the atom becoming an ion. Ions can be either positive when electrons are lost or negative when electrons are gained. Part C In the classical view of the atom, Bohr pictured electrons orbiting the positively charged nucleus similar to how the planets orbit the Sun. While this picture was not entirely correct, it provides a good framework in which to make calculations about the energies of electrons. Different from the predictions of Newtonian mechanics, which allows any energy to be possible, Bohr described the electron orbits (now called orbitals) as having specific energies. Rank the following electron energy states according to their electron energies. Rank from highest to lowest energies. Hint 1. What are the definitions of orbital, ground state, and excited state? Define orbital, ground state, and excited state. loss of an electron loss of a proton loss of a neutron gain of an electron gain of a proton gain of a neutron electron proton neutron Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 3 of 14 5/21/2014 8:02 PM Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. ANSWER: Hint 2. How does the state change when an electron absorbs energy? Electrons can absorb energy either from light radiation or from collisions with other atoms. If an electron is in the first excited energy state and absorbs enough energy to go to the next higher energy state, into what state will the electron transition? ANSWER: ANSWER: the ground state the second excited state the third excited state Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 4 of 14 5/21/2014 8:02 PM Correct Excited states refer to the energy of an electron. The higher the state, the higher the energy of the electron. The electron energies of each orbital are fixed. The energy required for an electron to transition between each orbital is an exact value, corresponding to the difference between the orbital energies. Any energy more or less than these precise differences cannot be used by the electron to make a transition; only the energies equal to the full values can induce a transition. Part D The Bohr model accounted for most of the general characteristics of the atom. However, the modern model based on quantum mechanics explains that, although the energy of each orbital is fixed, the orbital radius is actually an average distance. The result is a “cloud” where the electron is most likely to be located. The following is an image of an atom of hydrogen, consisting of one proton, zero neutrons, and one electron. When an electron is excited to different energy levels, the radius from the nucleus also changes. Rank the following electron energy states according to the average distance of the electron from the nucleus. Rank from largest to smallest distances. Hint 1. What is the relationship between electron orbital distance and electron energy? Rank the following general electron energies from largest to smallest electron orbital distances. Rank from largest to smallest orbital distances. ANSWER: ANSWER: Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 5 of 14 5/21/2014 8:02 PM Correct Excited states refer to the energy state of an electron. The higher the state, the higher the energy and the greater the distance of the electron from the nucleus. Due to the attractive force between the negatively charged electron and the positively charged nucleus, the electron requires greater energies to overcome this attraction and achieve orbits at greater distances. Concept Review: The pH Scale Can you classify solutions as acidic, neutral, or basic? Part A Decide whether each label describes a solution that is acidic, neutral, or basic, and then drag it into the appropriate bin. ANSWER: Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 6 of 14 5/21/2014 8:02 PM Correct Activity: Carbohydrates Click here to complete this activity. Then answer the questions. Part A Glycogen is _____. ANSWER: Correct Animals store energy in the form of glycogen. a polysaccharide found in animals a source of saturated fat a polysaccharide found in plant cell walls the form in which plants store sugars a transport protein that carries oxygen Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 7 of 14 5/21/2014 8:02 PM Part B glucose + glucose —> _____ by _____. ANSWER: Correct Maltose is the disaccharide formed when two glucose molecules are linked by dehydration synthesis. Part C Which of these is a source of lactose? ANSWER: Correct Lactose is the sugar found in milk. Part D Which of these is a polysaccharide? ANSWER: Correct Cellulose is a carbohydrate composed of many monomers. Part E _____ is the most abundant organic compound on Earth. ANSWER: maltose + water … dehydration synthesis lactose + water … hydrolysis starch + water … dehydration synthesis sucrose + water … dehydration synthesis cellulose + water … hydrolysis potatoes sugar beets sugar cane starch milk sucrose lactose glucose galactose cellulose Cellulose Lactose Starch Glucose Glycogen Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 8 of 14 5/21/2014 8:02 PM Correct Cellulose, a component of plant cell walls, is the most abundant organic compound found on earth. Activity: Protein Structure Click here to complete this activity. Then answer the questions. Part A Proteins are polymers of _____. ANSWER: Correct Proteins are polymers of amino acids. Part B What type of bond joins the monomers in a protein’s primary structure? ANSWER: Correct The amino acids of a protein are linked by peptide bonds. Part C Which of these illustrates the secondary structure of a protein? ANSWER: nucleotides CH2O units glycerol hydrocarbons amino acids ionic hydrogen hydrophobic S—S peptide Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 9 of 14 5/21/2014 8:02 PM Correct Alpha helices and beta pleated sheets are characteristic of a protein’s secondary structure. Part D The secondary structure of a protein results from _____. ANSWER: Correct Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges. Part E Tertiary structure is NOT directly dependent on _____. ANSWER: bonds between sulfur atoms peptide bonds hydrogen bonds hydrophobic interactions ionic bonds hydrophobic interactions ionic bonds hydrogen bonds peptide bonds bonds between sulfur atoms Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 10 of 14 5/21/2014 8:02 PM Correct Peptide bonds link together the amino acids of a protein’s primary structure. Activity: Lipids Click here to complete this activity. Then answer the questions. Part A Which of these is NOT a lipid? ANSWER: Correct RNA is a nucleic acid Part B This figure is an example of a(n) _____. ANSWER: Correct The fatty acid tails lack double bonds. steroids phospholipid RNA cholesterol wax steroid unsaturated fat nucleic acid protein saturated fat Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 11 of 14 5/21/2014 8:02 PM Part C Which of these is a phospholipid? ANSWER: Correct Phospholipids are composed of a phosphate group, a glycerol, and fatty acids. Part D Which of these is rich in unsaturated fats? ANSWER: Correct Olive oil is a plant oil, and most plant oils are rich in unsaturated fats. Part E beef fat lard butter olive oil a fat that is solid at room temperature Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 12 of 14 5/21/2014 8:02 PM A function of cholesterol that does not harm health is its role _____. ANSWER: Correct Cholesterol is an important component of animal cell membranes. Concept Review: Types of Macromolecules Can you identify characteristics of proteins, nucleic acids, and carbohydrates? Part A Decide whether each label describes proteins, nucleic acids, or carbohydrates, and then drag it into the appropriate bin. ANSWER: Correct Concept Review: Earth’s Interior Layers Can you identify characteristics of Earth’s interior layers? Part A Drag the labels to the appropriate targets. ANSWER: as a component of animal cell membranes in calcium and phosphate metabolism All of cholesterol’s effects cause the body harm. as the most abundant male sex hormone as the primary female sex hormone Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 13 of 14 5/21/2014 8:02 PM Correct Score Summary: Your score on this assignment is 99.6%. You received 31.87 out of a possible total of 32 points. Chapter 03 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 14 of 14 5/21/2014 8:02 PM

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Assignment 10 Due: 11:59pm on Wednesday, April 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Conceptual Question 12.3 Part A The figure shows three rotating disks, all of equal mass. Rank in order, from largest to smallest, their rotational kinetic energies to . Rank from largest to smallest. To rank items as equivalent, overlap them. ANSWER: Ka Kc Correct Conceptual Question 12.6 You have two steel solid spheres. Sphere 2 has twice the radius of sphere 1. Part A By what factor does the moment of inertia of sphere 2 exceed the moment of inertia of sphere 1? ANSWER: I2 I1 Correct Problem 12.2 A high-speed drill reaches 2500 in 0.59 . Part A What is the drill’s angular acceleration? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B Through how many revolutions does it turn during this first 0.59 ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct I2/I1 = 32 rpm s  = 440 rad s2 s  = 12 rev Constant Angular Acceleration in the Kitchen Dario, a prep cook at an Italian restaurant, spins a salad spinner and observes that it rotates 20.0 times in 5.00 seconds and then stops spinning it. The salad spinner rotates 6.00 more times before it comes to rest. Assume that the spinner slows down with constant angular acceleration. Part A What is the angular acceleration of the salad spinner as it slows down? Express your answer numerically in degrees per second per second. Hint 1. How to approach the problem Recall from your study of kinematics the three equations of motion derived for systems undergoing constant linear acceleration. You are now studying systems undergoing constant angular acceleration and will need to work with the three analogous equations of motion. Collect your known quantities and then determine which of the angular kinematic equations is appropriate to find the angular acceleration . Hint 2. Find the angular velocity of the salad spinner while Dario is spinning it What is the angular velocity of the salad spinner as Dario is spinning it? Express your answer numerically in degrees per second. Hint 1. Converting rotations to degrees When the salad spinner spins through one revolution, it turns through 360 degrees. ANSWER: Hint 3. Find the angular distance the salad spinner travels as it comes to rest Through how many degrees does the salad spinner rotate as it comes to rest? Express your answer numerically in degrees. Hint 1. Converting rotations to degrees  0 = 1440 degrees/s  =  − 0 One revolution is equivalent to 360 degrees. ANSWER: Hint 4. Determine which equation to use You know the initial and final velocities of the system and the angular distance through which the spinner rotates as it comes to a stop. Which equation should be used to solve for the unknown constant angular acceleration ? ANSWER: ANSWER: Correct Part B How long does it take for the salad spinner to come to rest? Express your answer numerically in seconds.  = 2160 degrees   = 0 + 0t+  1 2 t2  = 0 + t = + 2( − ) 2 20 0  = -480 degrees/s2 Hint 1. How to approach the problem Again, you will need the equations of rotational kinematics that apply to situations of constant angular acceleration. Collect your known quantities and then determine which of the angular kinematic equations is appropriate to find . Hint 2. Determine which equation to use You have the initial and final velocities of the system and the angular acceleration, which you found in the previous part. Which is the best equation to use to solve for the unknown time ? ANSWER: ANSWER: Correct ± A Spinning Electric Fan An electric fan is turned off, and its angular velocity decreases uniformly from 540 to 250 in a time interval of length 4.40 . Part A Find the angular acceleration in revolutions per second per second. Hint 1. Average acceleration Recall that if the angular velocity decreases uniformly, the angular acceleration will remain constant. Therefore, the angular acceleration is just the total change in angular velocity divided by t t  = 0 + 0t+  1 2 t2  = 0 + t = + 2( − ) 2 20 0 t = 3.00 s rev/min rev/min s  the total change in time. Be careful of the sign of the angular acceleration. ANSWER: Correct Part B Find the number of revolutions made by the fan blades during the time that they are slowing down in Part A. Hint 1. Determine the correct kinematic equation Which of the following kinematic equations is best suited to this problem? Here and are the initial and final angular velocities, is the elapsed time, is the constant angular acceleration, and and are the initial and final angular displacements. Hint 1. How to chose the right equation Notice that you were given in the problem introduction the initial and final speeds, as well as the length of time between them. In this problem, you are asked to find the number of revolutions (which here is the change in angular displacement, ). If you already found the angular acceleration in Part A, you could use that as well, but you would end up using a more complex equation. Also, in general, it is somewhat favorable to use given quantities instead of quantities that you have calculated. ANSWER:  = -1.10 rev/s2 0  t  0   − 0  = 0 + t  = 0 + t+  1 2 t2 = + 2( − ) 2 20 0 − 0 = (+ )t 1 2 0 ANSWER: Correct Part C How many more seconds are required for the fan to come to rest if the angular acceleration remains constant at the value calculated in Part A? Hint 1. Finding the total time for spin down To find the total time for spin down, just calculate when the velocity will equal zero. This is accomplished by setting the initial velocity plus the acceleration multipled by the time equal to zero and then solving for the time. One can then just subtract the time it took to reach 250 from the total time. Be careful of your signs when you set up the equation. ANSWER: Correct Problem 12.8 A 100 ball and a 230 ball are connected by a 34- -long, massless, rigid rod. The balls rotate about their center of mass at 130 . Part A What is the speed of the 100 ball? Express your answer to two significant figures and include the appropriate units. ANSWER: 29.0 rev rev/min 3.79 s g g cm rpm g Correct Problem 12.10 A thin, 60.0 disk with a diameter of 9.00 rotates about an axis through its center with 0.200 of kinetic energy. Part A What is the speed of a point on the rim? Express your answer with the appropriate units. ANSWER: Correct Problem 12.12 A drum major twirls a 95- -long, 470 baton about its center of mass at 150 . Part A What is the baton’s rotational kinetic energy? Express your answer to two significant figures and include the appropriate units. ANSWER: v = 3.2 ms g cm J 3.65 ms cm g rpm K = 4.4 J Correct Net Torque on a Pulley The figure below shows two blocks suspended by a cord over a pulley. The mass of block B is twice the mass of block A, while the mass of the pulley is equal to the mass of block A. The blocks are let free to move and the cord moves on the pulley without slipping or stretching. There is no friction in the pulley axle, and the cord’s weight can be ignored. Part A Which of the following statements correctly describes the system shown in the figure? Check all that apply. Hint 1. Conditions for equilibrium If the blocks had the same mass, the system would be in equilibrium. The blocks would have zero acceleration and the tension in each part of the cord would equal the weight of each block. Both parts of the cord would then pull with equal force on the pulley, resulting in a zero net torque and no rotation of the pulley. Is this still the case in the current situation where block B has twice the mass of block A? Hint 2. Rotational analogue of Newton’s second law The net torque of all the forces acting on a rigid body is proportional to the angular acceleration of the body net  and is given by , where is the moment of inertia of the body. Hint 3. Relation between linear and angular acceleration A particle that rotates with angular acceleration has linear acceleration equal to , where is the distance of the particle from the axis of rotation. In the present case, where there is no slipping or stretching of the cord, the cord and the pulley must move together at the same speed. Therefore, if the cord moves with linear acceleration , the pulley must rotate with angular acceleration , where is the radius of the pulley. ANSWER: Correct Part B What happens when block B moves downward? Hint 1. How to approach the problem To determine whether the tensions in both parts of the cord are equal, it is convenient to write a mathematical expression for the net torque on the pulley. This will allow you to relate the tensions in the cord to the pulley’s angular acceleration. Hint 2. Find the net torque on the pulley Let’s assume that the tensions in both parts of the cord are different. Let be the tension in the right cord and the tension in the left cord. If is the radius of the pulley, what is the net torque acting on the pulley? Take the positive sense of rotation to be counterclockwise. Express your answer in terms of , , and . net = I I  a a = R R a  = a R R The acceleration of the blocks is zero. The net torque on the pulley is zero. The angular acceleration of the pulley is nonzero. T1 T2 R net T1 T2 R Hint 1. Torque The torque of a force with respect to a point is defined as the product of the magnitude times the perpendicular distance between the line of action of and the point . In other words, . ANSWER: ANSWER: Correct Note that if the pulley were stationary (as in many systems where only linear motion is studied), then the tensions in both parts of the cord would be equal. However, if the pulley rotates with a certain angular acceleration, as in the present situation, the tensions must be different. If they were equal, the pulley could not have an angular acceleration. Problem 12.18 Part A In the figure , what is the magnitude of net torque about the axle? Express your answer to two significant figures and include the appropriate units.  F  O F l F  O  = Fl net = R(T2 − T1 ) The left cord pulls on the pulley with greater force than the right cord. The left and right cord pull with equal force on the pulley. The right cord pulls on the pulley with greater force than the left cord. ANSWER: Correct Part B What is the direction of net torque about the axle? ANSWER: Correct Problem 12.22 An athlete at the gym holds a 3.5 steel ball in his hand. His arm is 78 long and has a mass of 3.6 . Assume the center of mass of the arm is at the geometrical center of the arm. Part A What is the magnitude of the torque about his shoulder if he holds his arm straight out to his side, parallel to the floor? Express your answer to two significant figures and include the appropriate units.  = 0.20 Nm Clockwise Counterclockwise kg cm kg ANSWER: Correct Part B What is the magnitude of the torque about his shoulder if he holds his arm straight, but below horizontal? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Parallel Axis Theorem The parallel axis theorem relates , the moment of inertia of an object about an axis passing through its center of mass, to , the moment of inertia of the same object about a parallel axis passing through point p. The mathematical statement of the theorem is , where is the perpendicular distance from the center of mass to the axis that passes through point p, and is the mass of the object. Part A Suppose a uniform slender rod has length and mass . The moment of inertia of the rod about about an axis that is perpendicular to the rod and that passes through its center of mass is given by . Find , the moment of inertia of the rod with respect to a parallel axis through one end of the rod. Express in terms of and . Use fractions rather than decimal numbers in your answer. Hint 1. Find the distance from the axis to the center of mass Find the distance appropriate to this problem. That is, find the perpendicular distance from the center of mass of the rod to the axis passing through one end of the rod.  = 41 Nm 45  = 29 Nm Icm Ip Ip = Icm + Md2 d M L m Icm = m 1 12 L2 Iend Iend m L d ANSWER: ANSWER: Correct Part B Now consider a cube of mass with edges of length . The moment of inertia of the cube about an axis through its center of mass and perpendicular to one of its faces is given by . Find , the moment of inertia about an axis p through one of the edges of the cube Express in terms of and . Use fractions rather than decimal numbers in your answer. Hint 1. Find the distance from the axis to the axis Find the perpendicular distance from the center of mass axis to the new edge axis (axis labeled p in the figure). ANSWER: d = L 2 Iend = mL2 3 m a Icm Icm = m 1 6 a2 Iedge Iedge m a o p d ANSWER: Correct Problem 12.26 Starting from rest, a 12- -diameter compact disk takes 2.9 to reach its operating angular velocity of 2000 . Assume that the angular acceleration is constant. The disk’s moment of inertia is . Part A How much torque is applied to the disk? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How many revolutions does it make before reaching full speed? Express your answer using two significant figures. ANSWER: d = a 2 Iedge = 2ma2 3 cm s rpm 2.5 × 10−5 kg m2 = 1.8×10−3  Nm Correct Problem 12.23 An object’s moment of inertia is 2.20 . Its angular velocity is increasing at the rate of 3.70 . Part A What is the total torque on the object? ANSWER: Correct Problem 12.31 A 5.1 cat and a 2.5 bowl of tuna fish are at opposite ends of the 4.0- -long seesaw. N = 48 rev kgm2 rad/s2 8.14 N  m kg kg m Part A How far to the left of the pivot must a 3.8 cat stand to keep the seesaw balanced? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Static Equilibrium of the Arm You are able to hold out your arm in an outstretched horizontal position because of the action of the deltoid muscle. Assume the humerus bone has a mass , length and its center of mass is a distance from the scapula. (For this problem ignore the rest of the arm.) The deltoid muscle attaches to the humerus a distance from the scapula. The deltoid muscle makes an angle of with the horizontal, as shown. Use throughout the problem. Part A kg d = 1.4 m M1 = 3.6 kg L = 0.66 m L1 = 0.33 m L2 = 0.15 m  = 17 g = 9.8 m/s2 Find the tension in the deltoid muscle. Express the tension in newtons, to the nearest integer. Hint 1. Nature of the problem Remember that this is a statics problem, so all forces and torques are balanced (their sums equal zero). Hint 2. Origin of torque Calculate the torque about the point at which the arm attaches to the rest of the body. This allows one to balance the torques without having to worry about the undefined forces at this point. Hint 3. Adding up the torques Add up the torques about the point in which the humerus attaches to the body. Answer in terms of , , , , , and . Remember that counterclockwise torque is positive. ANSWER: ANSWER: Correct Part B Using the conditions for static equilibrium, find the magnitude of the vertical component of the force exerted by the scapula on the humerus (where the humerus attaches to the rest of the body). Express your answer in newtons, to the nearest integer. T L1 L2 M1 g T  total = 0 = L1M1g − Tsin()L2 T = 265 N Fy Hint 1. Total forces involved Recall that there are three vertical forces in this problem: the force of gravity acting on the bone, the force from the vertical component of the muscle tension, and the force exerted by the scapula on the humerus (where it attaches to the rest of the body). ANSWER: Correct Part C Now find the magnitude of the horizontal component of the force exerted by the scapula on the humerus. Express your answer in newtons, to the nearest integer. ANSWER: Correct ± Moments around a Rod A rod is bent into an L shape and attached at one point to a pivot. The rod sits on a frictionless table and the diagram is a view from above. This means that gravity can be ignored for this problem. There are three forces that are applied to the rod at different points and angles: , , and . Note that the dimensions of the bent rod are in centimeters in the figure, although the answers are requested in SI units (kilograms, meters, seconds). |Fy| = 42 N Fx |Fx| = 254 N F 1 F  2 F  3 Part A If and , what does the magnitude of have to be for there to be rotational equilibrium? Answer numerically in newtons to two significant figures. Hint 1. Finding torque about pivot from What is the magnitude of the torque | | provided by around the pivot point? Give your answer numerically in newton-meters to two significant figures. ANSWER: ANSWER: Correct Part B If the L-shaped rod has a moment of inertia , , , and again , how long a time would it take for the object to move through ( /4 radians)? Assume that as the object starts to move, each force moves with the object so as to retain its initial angle relative to the object. Express the time in seconds to two significant figures. F3 = 0 F1 = 12 N F 2 F 1   1 F  1 |  1 | = 0.36 N  m F2 = 4.5 N I = 9 kg m2 F1 = 12 N F2 = 27 N F3 = 0 t 45  Hint 1. Find the net torque about the pivot What is the magnitude of the total torque around the pivot point? Answer numerically in newton-meters to two significant figures. ANSWER: Hint 2. Calculate Given the total torque around the pivot point, what is , the magnitude of the angular acceleration? Express your answer numerically in radians per second squared to two significant figures. Hint 1. Equation for If you know the magnitude of the total torque ( ) and the rotational inertia ( ), you can then find the rotational acceleration ( ) from ANSWER: Hint 3. Description of angular kinematics Now that you know the angular acceleration, this is a problem in rotational kinematics; find the time needed to go through a given angle . For constant acceleration ( ) and starting with (where is angular speed) the relation is given by which is analogous to the expression for linear displacement ( ) with constant acceleration ( ) starting from rest, | p ivot| | p ivot| = 1.8 N  m    vot Ivot  pivot = Ipivot.  = 0.20 radians/s2    = 0   = 1  , 2 t2 x a . ANSWER: Correct Part C Now consider the situation in which and , but now a force with nonzero magnitude is acting on the rod. What does have to be to obtain equilibrium? Give a numerical answer, without trigonometric functions, in newtons, to two significant figures. Hint 1. Find the required component of Only the tangential (perpendicular) component of (call it ) provides a torque. What is ? Answer in terms of . You will need to evaluate any trigonometric functions. ANSWER: ANSWER: Correct x = 1 a 2 t2 t = 2.8 s F1 = 12 N F2 = 0 F3 F3 F 3 F  3 F3t F3t F3 F3t = 1 2 F3 F3 = 9.0 N Problem 12.32 A car tire is 55.0 in diameter. The car is traveling at a speed of 24.0 . Part A What is the tire’s rotation frequency, in rpm? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Part B What is the speed of a point at the top edge of the tire? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Part C What is the speed of a point at the bottom edge of the tire? Express your answer as an integer and include the appropriate units. ANSWER: cm m/s 833 rpm 48.0 ms 0 ms Correct Problem 12.33 A 460 , 8.00-cm-diameter solid cylinder rolls across the floor at 1.30 . Part A What is the can’s kinetic energy? Express your answer with the appropriate units. ANSWER: Correct Problem 12.45 Part A What is the magnitude of the angular momentum of the 780 rotating bar in the figure ? g m/s 0.583 J g ANSWER: Correct Part B What is the direction of the angular momentum of the bar ? ANSWER: Correct Problem 12.46 Part A What is the magnitude of the angular momentum of the 2.20 , 4.60-cm-diameter rotating disk in the figure ? 3.27 kgm2/s into the page out of the page kg ANSWER: Correct Part B What is its direction? ANSWER: Correct Problem 12.60 A 3.0- -long ladder, as shown in the following figure, leans against a frictionless wall. The coefficient of static friction between the ladder and the floor is 0.46. 3.66×10−2 kgm /s 2 x direction -x direction y direction -y direction z direction -z direction m Part A What is the minimum angle the ladder can make with the floor without slipping? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 12.61 The 3.0- -long, 90 rigid beam in the following figure is supported at each end. An 70 student stands 2.0 from support 1.  = 47 m kg kg m Part A How much upward force does the support 1 exert on the beam? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How much upward force does the support 2 exert on the beam? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Enhanced EOC: Problem 12.63 A 44 , 5.5- -long beam is supported, but not attached to, the two posts in the figure . A 22 boy starts walking along the beam. You may want to review ( pages 330 – 334) . For help with math skills, you may want to review: F1 = 670 N F2 = 900 N kg m kg The Vector Cross Product Part A How close can he get to the right end of the beam without it falling over? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture of the four forces acting on the beam, indicating both their direction and the place on the beam that the forces are acting. Choose a coordinate system with a direction for the axis along the beam, and indicate the position of the boy. What is the net force on the beam if it is stationary? Just before the beam tips, the force of the left support on the beam is zero. Using the zero net force condition, what is the force due to the right support just before the beam tips? For the beam to remain stationary, what must be zero besides the net force on the beam? Choose a point on the beam, and compute the net torque on the beam about that point. Be sure to choose a positive direction for the rotation axis and therefore the torques. Using the zero torque condition, what is the position of the boy on the beam just prior to tipping? How far is this position from the right edge of the beam? ANSWER: Correct d = 2.0 m Problem 12.68 Flywheels are large, massive wheels used to store energy. They can be spun up slowly, then the wheel’s energy can be released quickly to accomplish a task that demands high power. An industrial flywheel has a 1.6 diameter and a mass of 270 . Its maximum angular velocity is 1500 . Part A A motor spins up the flywheel with a constant torque of 54 . How long does it take the flywheel to reach top speed? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How much energy is stored in the flywheel? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C The flywheel is disconnected from the motor and connected to a machine to which it will deliver energy. Half the energy stored in the flywheel is delivered in 2.2 . What is the average power delivered to the machine? Express your answer to two significant figures and include the appropriate units. ANSWER: m kg rpm N  m t = 250 s = 1.1×106 E J s Correct Part D How much torque does the flywheel exert on the machine? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 12.71 The 3.30 , 40.0-cm-diameter disk in the figure is spinning at 350 . Part A How much friction force must the brake apply to the rim to bring the disk to a halt in 2.10 ? P = 2.4×105 W  = 1800 Nm kg rpm s Express your answer with the appropriate units. ANSWER: Correct Problem 12.74 A 5.0 , 60- -diameter cylinder rotates on an axle passing through one edge. The axle is parallel to the floor. The cylinder is held with the center of mass at the same height as the axle, then released. Part A What is the magnitude of the cylinder’s initial angular acceleration? Express your answer to two significant figures and include the appropriate units. ANSWER: 5.76 N kg cm  = 22 rad s2 Correct Part B What is the magnitude of the cylinder’s angular velocity when it is directly below the axle? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 12.82 A 45 figure skater is spinning on the toes of her skates at 0.90 . Her arms are outstretched as far as they will go. In this orientation, the skater can be modeled as a cylindrical torso (40 , 20 average diameter, 160 tall) plus two rod-like arms (2.5 each, 67 long) attached to the outside of the torso. The skater then raises her arms straight above her head, where she appears to be a 45 , 20- -diameter, 200- -tall cylinder. Part A What is her new rotation frequency, in revolutions per second? Express your answer to two significant figures and include the appropriate units. ANSWER: Incorrect; Try Again Score Summary:  = 6.6 rad s kg rev/s kg cm cm kg cm kg cm cm 2 = Your score on this assignment is 95.7%. You received 189.42 out of a possible total of 198 points.

Assignment 10 Due: 11:59pm on Wednesday, April 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Conceptual Question 12.3 Part A The figure shows three rotating disks, all of equal mass. Rank in order, from largest to smallest, their rotational kinetic energies to . Rank from largest to smallest. To rank items as equivalent, overlap them. ANSWER: Ka Kc Correct Conceptual Question 12.6 You have two steel solid spheres. Sphere 2 has twice the radius of sphere 1. Part A By what factor does the moment of inertia of sphere 2 exceed the moment of inertia of sphere 1? ANSWER: I2 I1 Correct Problem 12.2 A high-speed drill reaches 2500 in 0.59 . Part A What is the drill’s angular acceleration? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B Through how many revolutions does it turn during this first 0.59 ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct I2/I1 = 32 rpm s  = 440 rad s2 s  = 12 rev Constant Angular Acceleration in the Kitchen Dario, a prep cook at an Italian restaurant, spins a salad spinner and observes that it rotates 20.0 times in 5.00 seconds and then stops spinning it. The salad spinner rotates 6.00 more times before it comes to rest. Assume that the spinner slows down with constant angular acceleration. Part A What is the angular acceleration of the salad spinner as it slows down? Express your answer numerically in degrees per second per second. Hint 1. How to approach the problem Recall from your study of kinematics the three equations of motion derived for systems undergoing constant linear acceleration. You are now studying systems undergoing constant angular acceleration and will need to work with the three analogous equations of motion. Collect your known quantities and then determine which of the angular kinematic equations is appropriate to find the angular acceleration . Hint 2. Find the angular velocity of the salad spinner while Dario is spinning it What is the angular velocity of the salad spinner as Dario is spinning it? Express your answer numerically in degrees per second. Hint 1. Converting rotations to degrees When the salad spinner spins through one revolution, it turns through 360 degrees. ANSWER: Hint 3. Find the angular distance the salad spinner travels as it comes to rest Through how many degrees does the salad spinner rotate as it comes to rest? Express your answer numerically in degrees. Hint 1. Converting rotations to degrees  0 = 1440 degrees/s  =  − 0 One revolution is equivalent to 360 degrees. ANSWER: Hint 4. Determine which equation to use You know the initial and final velocities of the system and the angular distance through which the spinner rotates as it comes to a stop. Which equation should be used to solve for the unknown constant angular acceleration ? ANSWER: ANSWER: Correct Part B How long does it take for the salad spinner to come to rest? Express your answer numerically in seconds.  = 2160 degrees   = 0 + 0t+  1 2 t2  = 0 + t = + 2( − ) 2 20 0  = -480 degrees/s2 Hint 1. How to approach the problem Again, you will need the equations of rotational kinematics that apply to situations of constant angular acceleration. Collect your known quantities and then determine which of the angular kinematic equations is appropriate to find . Hint 2. Determine which equation to use You have the initial and final velocities of the system and the angular acceleration, which you found in the previous part. Which is the best equation to use to solve for the unknown time ? ANSWER: ANSWER: Correct ± A Spinning Electric Fan An electric fan is turned off, and its angular velocity decreases uniformly from 540 to 250 in a time interval of length 4.40 . Part A Find the angular acceleration in revolutions per second per second. Hint 1. Average acceleration Recall that if the angular velocity decreases uniformly, the angular acceleration will remain constant. Therefore, the angular acceleration is just the total change in angular velocity divided by t t  = 0 + 0t+  1 2 t2  = 0 + t = + 2( − ) 2 20 0 t = 3.00 s rev/min rev/min s  the total change in time. Be careful of the sign of the angular acceleration. ANSWER: Correct Part B Find the number of revolutions made by the fan blades during the time that they are slowing down in Part A. Hint 1. Determine the correct kinematic equation Which of the following kinematic equations is best suited to this problem? Here and are the initial and final angular velocities, is the elapsed time, is the constant angular acceleration, and and are the initial and final angular displacements. Hint 1. How to chose the right equation Notice that you were given in the problem introduction the initial and final speeds, as well as the length of time between them. In this problem, you are asked to find the number of revolutions (which here is the change in angular displacement, ). If you already found the angular acceleration in Part A, you could use that as well, but you would end up using a more complex equation. Also, in general, it is somewhat favorable to use given quantities instead of quantities that you have calculated. ANSWER:  = -1.10 rev/s2 0  t  0   − 0  = 0 + t  = 0 + t+  1 2 t2 = + 2( − ) 2 20 0 − 0 = (+ )t 1 2 0 ANSWER: Correct Part C How many more seconds are required for the fan to come to rest if the angular acceleration remains constant at the value calculated in Part A? Hint 1. Finding the total time for spin down To find the total time for spin down, just calculate when the velocity will equal zero. This is accomplished by setting the initial velocity plus the acceleration multipled by the time equal to zero and then solving for the time. One can then just subtract the time it took to reach 250 from the total time. Be careful of your signs when you set up the equation. ANSWER: Correct Problem 12.8 A 100 ball and a 230 ball are connected by a 34- -long, massless, rigid rod. The balls rotate about their center of mass at 130 . Part A What is the speed of the 100 ball? Express your answer to two significant figures and include the appropriate units. ANSWER: 29.0 rev rev/min 3.79 s g g cm rpm g Correct Problem 12.10 A thin, 60.0 disk with a diameter of 9.00 rotates about an axis through its center with 0.200 of kinetic energy. Part A What is the speed of a point on the rim? Express your answer with the appropriate units. ANSWER: Correct Problem 12.12 A drum major twirls a 95- -long, 470 baton about its center of mass at 150 . Part A What is the baton’s rotational kinetic energy? Express your answer to two significant figures and include the appropriate units. ANSWER: v = 3.2 ms g cm J 3.65 ms cm g rpm K = 4.4 J Correct Net Torque on a Pulley The figure below shows two blocks suspended by a cord over a pulley. The mass of block B is twice the mass of block A, while the mass of the pulley is equal to the mass of block A. The blocks are let free to move and the cord moves on the pulley without slipping or stretching. There is no friction in the pulley axle, and the cord’s weight can be ignored. Part A Which of the following statements correctly describes the system shown in the figure? Check all that apply. Hint 1. Conditions for equilibrium If the blocks had the same mass, the system would be in equilibrium. The blocks would have zero acceleration and the tension in each part of the cord would equal the weight of each block. Both parts of the cord would then pull with equal force on the pulley, resulting in a zero net torque and no rotation of the pulley. Is this still the case in the current situation where block B has twice the mass of block A? Hint 2. Rotational analogue of Newton’s second law The net torque of all the forces acting on a rigid body is proportional to the angular acceleration of the body net  and is given by , where is the moment of inertia of the body. Hint 3. Relation between linear and angular acceleration A particle that rotates with angular acceleration has linear acceleration equal to , where is the distance of the particle from the axis of rotation. In the present case, where there is no slipping or stretching of the cord, the cord and the pulley must move together at the same speed. Therefore, if the cord moves with linear acceleration , the pulley must rotate with angular acceleration , where is the radius of the pulley. ANSWER: Correct Part B What happens when block B moves downward? Hint 1. How to approach the problem To determine whether the tensions in both parts of the cord are equal, it is convenient to write a mathematical expression for the net torque on the pulley. This will allow you to relate the tensions in the cord to the pulley’s angular acceleration. Hint 2. Find the net torque on the pulley Let’s assume that the tensions in both parts of the cord are different. Let be the tension in the right cord and the tension in the left cord. If is the radius of the pulley, what is the net torque acting on the pulley? Take the positive sense of rotation to be counterclockwise. Express your answer in terms of , , and . net = I I  a a = R R a  = a R R The acceleration of the blocks is zero. The net torque on the pulley is zero. The angular acceleration of the pulley is nonzero. T1 T2 R net T1 T2 R Hint 1. Torque The torque of a force with respect to a point is defined as the product of the magnitude times the perpendicular distance between the line of action of and the point . In other words, . ANSWER: ANSWER: Correct Note that if the pulley were stationary (as in many systems where only linear motion is studied), then the tensions in both parts of the cord would be equal. However, if the pulley rotates with a certain angular acceleration, as in the present situation, the tensions must be different. If they were equal, the pulley could not have an angular acceleration. Problem 12.18 Part A In the figure , what is the magnitude of net torque about the axle? Express your answer to two significant figures and include the appropriate units.  F  O F l F  O  = Fl net = R(T2 − T1 ) The left cord pulls on the pulley with greater force than the right cord. The left and right cord pull with equal force on the pulley. The right cord pulls on the pulley with greater force than the left cord. ANSWER: Correct Part B What is the direction of net torque about the axle? ANSWER: Correct Problem 12.22 An athlete at the gym holds a 3.5 steel ball in his hand. His arm is 78 long and has a mass of 3.6 . Assume the center of mass of the arm is at the geometrical center of the arm. Part A What is the magnitude of the torque about his shoulder if he holds his arm straight out to his side, parallel to the floor? Express your answer to two significant figures and include the appropriate units.  = 0.20 Nm Clockwise Counterclockwise kg cm kg ANSWER: Correct Part B What is the magnitude of the torque about his shoulder if he holds his arm straight, but below horizontal? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Parallel Axis Theorem The parallel axis theorem relates , the moment of inertia of an object about an axis passing through its center of mass, to , the moment of inertia of the same object about a parallel axis passing through point p. The mathematical statement of the theorem is , where is the perpendicular distance from the center of mass to the axis that passes through point p, and is the mass of the object. Part A Suppose a uniform slender rod has length and mass . The moment of inertia of the rod about about an axis that is perpendicular to the rod and that passes through its center of mass is given by . Find , the moment of inertia of the rod with respect to a parallel axis through one end of the rod. Express in terms of and . Use fractions rather than decimal numbers in your answer. Hint 1. Find the distance from the axis to the center of mass Find the distance appropriate to this problem. That is, find the perpendicular distance from the center of mass of the rod to the axis passing through one end of the rod.  = 41 Nm 45  = 29 Nm Icm Ip Ip = Icm + Md2 d M L m Icm = m 1 12 L2 Iend Iend m L d ANSWER: ANSWER: Correct Part B Now consider a cube of mass with edges of length . The moment of inertia of the cube about an axis through its center of mass and perpendicular to one of its faces is given by . Find , the moment of inertia about an axis p through one of the edges of the cube Express in terms of and . Use fractions rather than decimal numbers in your answer. Hint 1. Find the distance from the axis to the axis Find the perpendicular distance from the center of mass axis to the new edge axis (axis labeled p in the figure). ANSWER: d = L 2 Iend = mL2 3 m a Icm Icm = m 1 6 a2 Iedge Iedge m a o p d ANSWER: Correct Problem 12.26 Starting from rest, a 12- -diameter compact disk takes 2.9 to reach its operating angular velocity of 2000 . Assume that the angular acceleration is constant. The disk’s moment of inertia is . Part A How much torque is applied to the disk? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How many revolutions does it make before reaching full speed? Express your answer using two significant figures. ANSWER: d = a 2 Iedge = 2ma2 3 cm s rpm 2.5 × 10−5 kg m2 = 1.8×10−3  Nm Correct Problem 12.23 An object’s moment of inertia is 2.20 . Its angular velocity is increasing at the rate of 3.70 . Part A What is the total torque on the object? ANSWER: Correct Problem 12.31 A 5.1 cat and a 2.5 bowl of tuna fish are at opposite ends of the 4.0- -long seesaw. N = 48 rev kgm2 rad/s2 8.14 N  m kg kg m Part A How far to the left of the pivot must a 3.8 cat stand to keep the seesaw balanced? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Static Equilibrium of the Arm You are able to hold out your arm in an outstretched horizontal position because of the action of the deltoid muscle. Assume the humerus bone has a mass , length and its center of mass is a distance from the scapula. (For this problem ignore the rest of the arm.) The deltoid muscle attaches to the humerus a distance from the scapula. The deltoid muscle makes an angle of with the horizontal, as shown. Use throughout the problem. Part A kg d = 1.4 m M1 = 3.6 kg L = 0.66 m L1 = 0.33 m L2 = 0.15 m  = 17 g = 9.8 m/s2 Find the tension in the deltoid muscle. Express the tension in newtons, to the nearest integer. Hint 1. Nature of the problem Remember that this is a statics problem, so all forces and torques are balanced (their sums equal zero). Hint 2. Origin of torque Calculate the torque about the point at which the arm attaches to the rest of the body. This allows one to balance the torques without having to worry about the undefined forces at this point. Hint 3. Adding up the torques Add up the torques about the point in which the humerus attaches to the body. Answer in terms of , , , , , and . Remember that counterclockwise torque is positive. ANSWER: ANSWER: Correct Part B Using the conditions for static equilibrium, find the magnitude of the vertical component of the force exerted by the scapula on the humerus (where the humerus attaches to the rest of the body). Express your answer in newtons, to the nearest integer. T L1 L2 M1 g T  total = 0 = L1M1g − Tsin()L2 T = 265 N Fy Hint 1. Total forces involved Recall that there are three vertical forces in this problem: the force of gravity acting on the bone, the force from the vertical component of the muscle tension, and the force exerted by the scapula on the humerus (where it attaches to the rest of the body). ANSWER: Correct Part C Now find the magnitude of the horizontal component of the force exerted by the scapula on the humerus. Express your answer in newtons, to the nearest integer. ANSWER: Correct ± Moments around a Rod A rod is bent into an L shape and attached at one point to a pivot. The rod sits on a frictionless table and the diagram is a view from above. This means that gravity can be ignored for this problem. There are three forces that are applied to the rod at different points and angles: , , and . Note that the dimensions of the bent rod are in centimeters in the figure, although the answers are requested in SI units (kilograms, meters, seconds). |Fy| = 42 N Fx |Fx| = 254 N F 1 F  2 F  3 Part A If and , what does the magnitude of have to be for there to be rotational equilibrium? Answer numerically in newtons to two significant figures. Hint 1. Finding torque about pivot from What is the magnitude of the torque | | provided by around the pivot point? Give your answer numerically in newton-meters to two significant figures. ANSWER: ANSWER: Correct Part B If the L-shaped rod has a moment of inertia , , , and again , how long a time would it take for the object to move through ( /4 radians)? Assume that as the object starts to move, each force moves with the object so as to retain its initial angle relative to the object. Express the time in seconds to two significant figures. F3 = 0 F1 = 12 N F 2 F 1   1 F  1 |  1 | = 0.36 N  m F2 = 4.5 N I = 9 kg m2 F1 = 12 N F2 = 27 N F3 = 0 t 45  Hint 1. Find the net torque about the pivot What is the magnitude of the total torque around the pivot point? Answer numerically in newton-meters to two significant figures. ANSWER: Hint 2. Calculate Given the total torque around the pivot point, what is , the magnitude of the angular acceleration? Express your answer numerically in radians per second squared to two significant figures. Hint 1. Equation for If you know the magnitude of the total torque ( ) and the rotational inertia ( ), you can then find the rotational acceleration ( ) from ANSWER: Hint 3. Description of angular kinematics Now that you know the angular acceleration, this is a problem in rotational kinematics; find the time needed to go through a given angle . For constant acceleration ( ) and starting with (where is angular speed) the relation is given by which is analogous to the expression for linear displacement ( ) with constant acceleration ( ) starting from rest, | p ivot| | p ivot| = 1.8 N  m    vot Ivot  pivot = Ipivot.  = 0.20 radians/s2    = 0   = 1  , 2 t2 x a . ANSWER: Correct Part C Now consider the situation in which and , but now a force with nonzero magnitude is acting on the rod. What does have to be to obtain equilibrium? Give a numerical answer, without trigonometric functions, in newtons, to two significant figures. Hint 1. Find the required component of Only the tangential (perpendicular) component of (call it ) provides a torque. What is ? Answer in terms of . You will need to evaluate any trigonometric functions. ANSWER: ANSWER: Correct x = 1 a 2 t2 t = 2.8 s F1 = 12 N F2 = 0 F3 F3 F 3 F  3 F3t F3t F3 F3t = 1 2 F3 F3 = 9.0 N Problem 12.32 A car tire is 55.0 in diameter. The car is traveling at a speed of 24.0 . Part A What is the tire’s rotation frequency, in rpm? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Part B What is the speed of a point at the top edge of the tire? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Part C What is the speed of a point at the bottom edge of the tire? Express your answer as an integer and include the appropriate units. ANSWER: cm m/s 833 rpm 48.0 ms 0 ms Correct Problem 12.33 A 460 , 8.00-cm-diameter solid cylinder rolls across the floor at 1.30 . Part A What is the can’s kinetic energy? Express your answer with the appropriate units. ANSWER: Correct Problem 12.45 Part A What is the magnitude of the angular momentum of the 780 rotating bar in the figure ? g m/s 0.583 J g ANSWER: Correct Part B What is the direction of the angular momentum of the bar ? ANSWER: Correct Problem 12.46 Part A What is the magnitude of the angular momentum of the 2.20 , 4.60-cm-diameter rotating disk in the figure ? 3.27 kgm2/s into the page out of the page kg ANSWER: Correct Part B What is its direction? ANSWER: Correct Problem 12.60 A 3.0- -long ladder, as shown in the following figure, leans against a frictionless wall. The coefficient of static friction between the ladder and the floor is 0.46. 3.66×10−2 kgm /s 2 x direction -x direction y direction -y direction z direction -z direction m Part A What is the minimum angle the ladder can make with the floor without slipping? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 12.61 The 3.0- -long, 90 rigid beam in the following figure is supported at each end. An 70 student stands 2.0 from support 1.  = 47 m kg kg m Part A How much upward force does the support 1 exert on the beam? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How much upward force does the support 2 exert on the beam? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Enhanced EOC: Problem 12.63 A 44 , 5.5- -long beam is supported, but not attached to, the two posts in the figure . A 22 boy starts walking along the beam. You may want to review ( pages 330 – 334) . For help with math skills, you may want to review: F1 = 670 N F2 = 900 N kg m kg The Vector Cross Product Part A How close can he get to the right end of the beam without it falling over? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture of the four forces acting on the beam, indicating both their direction and the place on the beam that the forces are acting. Choose a coordinate system with a direction for the axis along the beam, and indicate the position of the boy. What is the net force on the beam if it is stationary? Just before the beam tips, the force of the left support on the beam is zero. Using the zero net force condition, what is the force due to the right support just before the beam tips? For the beam to remain stationary, what must be zero besides the net force on the beam? Choose a point on the beam, and compute the net torque on the beam about that point. Be sure to choose a positive direction for the rotation axis and therefore the torques. Using the zero torque condition, what is the position of the boy on the beam just prior to tipping? How far is this position from the right edge of the beam? ANSWER: Correct d = 2.0 m Problem 12.68 Flywheels are large, massive wheels used to store energy. They can be spun up slowly, then the wheel’s energy can be released quickly to accomplish a task that demands high power. An industrial flywheel has a 1.6 diameter and a mass of 270 . Its maximum angular velocity is 1500 . Part A A motor spins up the flywheel with a constant torque of 54 . How long does it take the flywheel to reach top speed? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How much energy is stored in the flywheel? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C The flywheel is disconnected from the motor and connected to a machine to which it will deliver energy. Half the energy stored in the flywheel is delivered in 2.2 . What is the average power delivered to the machine? Express your answer to two significant figures and include the appropriate units. ANSWER: m kg rpm N  m t = 250 s = 1.1×106 E J s Correct Part D How much torque does the flywheel exert on the machine? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 12.71 The 3.30 , 40.0-cm-diameter disk in the figure is spinning at 350 . Part A How much friction force must the brake apply to the rim to bring the disk to a halt in 2.10 ? P = 2.4×105 W  = 1800 Nm kg rpm s Express your answer with the appropriate units. ANSWER: Correct Problem 12.74 A 5.0 , 60- -diameter cylinder rotates on an axle passing through one edge. The axle is parallel to the floor. The cylinder is held with the center of mass at the same height as the axle, then released. Part A What is the magnitude of the cylinder’s initial angular acceleration? Express your answer to two significant figures and include the appropriate units. ANSWER: 5.76 N kg cm  = 22 rad s2 Correct Part B What is the magnitude of the cylinder’s angular velocity when it is directly below the axle? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 12.82 A 45 figure skater is spinning on the toes of her skates at 0.90 . Her arms are outstretched as far as they will go. In this orientation, the skater can be modeled as a cylindrical torso (40 , 20 average diameter, 160 tall) plus two rod-like arms (2.5 each, 67 long) attached to the outside of the torso. The skater then raises her arms straight above her head, where she appears to be a 45 , 20- -diameter, 200- -tall cylinder. Part A What is her new rotation frequency, in revolutions per second? Express your answer to two significant figures and include the appropriate units. ANSWER: Incorrect; Try Again Score Summary:  = 6.6 rad s kg rev/s kg cm cm kg cm kg cm cm 2 = Your score on this assignment is 95.7%. You received 189.42 out of a possible total of 198 points.

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Chapter 05 Homework Due: 11:59pm on Friday, May 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Activity: Human Population Growth Click here to complete this activity. Then answer the questions. Part A Which of these was the first of the major events that stimulated an increase in the size of the human population? ANSWER: Correct The advent of agriculture is the first of the events listed here that stimulated an increase in the size of the human population. Part B Which of these was the second of the major events that stimulated an increase in the size of the human population? ANSWER: Correct The Industrial Revolution was the second of the major events that stimulated an increase in the size of the human population. Part C Which of these was the third of the major events that stimulated an increase in the size of the human population? ANSWER: Correct The advent of modern medicine is the third and most recent of the events listed here that have stimulated an increase in the population size of humans. the Industrial Revolution the advent of agriculture the discovery of antibiotics the bubonic plague the discovery of vaccines the discovery of vaccines the discovery of antibiotics the advent of agriculture the Industrial Revolution the bubonic plague the discovery of vaccines the advent of agriculture the discovery of antibiotics the discovery of vaccines and the discovery of antibiotics the Industrial Revolution Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 1 of 8 5/21/2014 8:00 PM Part D Currently, how large is the worldwide population of humans relative to Earth’s carrying capacity for humans? ANSWER: Correct Not knowing how technological innovations will affect the human population means there is insufficient information to answer this question. Activity: Analyzing Age-Structure Pyramids Click here to complete this activity. Then answer the questions. Part A Ignoring migration, the age structure of a human population likely to increase in size will have what shape? ANSWER: Correct This would mean that most individuals are in the prereproductive years. Such a population is expected to increase. Part B Ignoring migration, the age structure of a human population likely to decrease in size will have what shape? ANSWER: Correct In such a population the majority of individuals are in their postreproductive years. Such a population is expected to decrease. Part C Ignoring migration, the age structure diagram of a human population likely to maintain a relatively stable size will have what shape? There is insufficient information to answer this question. either at or above the carrying capacity below the carrying capacity above the carrying capacity at the carrying capacity Both an inverted pyramid and a rectangle tapering toward the top result in a population that increases in size. pyramid Both a pyramid and a rectangle tapering toward the top result in a population that increases in size. a rectangle tapering toward the top inverted pyramid pyramid Both an inverted pyramid and a rectangle tapering toward the top result in a population that decreases in size. Both a pyramid and a rectangle tapering toward the top result in a population that decreases in size. a rectangle tapering toward the top inverted pyramid Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 2 of 8 5/21/2014 8:00 PM ANSWER: Correct Such a population is expected to have a relatively stable size. GraphIt!: Age Pyramids and Population Growth Click here to complete the graphing activity. Then answer the questions. Part A – Question 1 The population of Greece is expected to _______. Hint 1. Review Step 2 of this activity. What shape does this population have? ANSWER: Correct Part B – Question 2 Assuming the current trend continues, in 30 years Greece will have more children than reproductive-age individuals. Hint 1. What age group will today’s newborns occupy in 2030? ANSWER: Correct Part C – Question 3 Assuming the current trend continues, in 30 years Greece will have more children than elderly members of the population. Hint 1. Both an inverted pyramid and a rectangle tapering toward the top result in a population that remains stable in size. pyramid Both a pyramid and a rectangle tapering toward the top result in a population that remains stable in size. inverted pyramid a rectangle tapering toward the top expand remain stable decline True False Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 3 of 8 5/21/2014 8:00 PM What age groups will today’s reproductive-age individuals occupy in 2030? ANSWER: Correct Part D – Question 4 Assuming the current trend continues, in 30 years Greece will have more reproductive-age individuals than children. ANSWER: Correct Part E – Question 5 Assuming the current trend continues, in 30 years Greece will have more elderly than reproductive-age individuals. ANSWER: Correct Part F – Question 6 Greece had more females than males in 2000. Which of the following is the most likely explanation for this? Hint 1. Which sex tends to live longer in the United States, males or females? ANSWER: Correct Part G – Question 7 The population of Colombia is currently _______. Hint 1. Review Step 2 of this activity. What shape does this population have? ANSWER: True False True False True False Females generally have a shorter life span than males. More females are born than males, and this difference remains throughout all age groups. There should be an equal number of males and females in every age group, so this is likely an error in the 2000 census for Greece. Males generally have a shorter life span than females. expanding stable declining Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 4 of 8 5/21/2014 8:00 PM Correct Part H – Question 8 Assuming the current trend continues, in 30 years Colombia will have more children than reproductive-age individuals. Hint 1. What age group will today’s newborns occupy in 2030? ANSWER: Correct Part I – Question 9 Assuming the current trend continues, in 30 years Colombia will have more children than elderly members of the population. Hint 1. What age groups will today’s reproductive-age individuals occupy in 2030? ANSWER: Correct Part J – Question 10 Assuming the current trend continues, in 30 years Colombia will have more reproductive-age individuals than children. ANSWER: Correct Part K – Question 11 Assuming the current trend continues, in 30 years Colombia will have more elderly than reproductive-age individuals. ANSWER: Correct Concept Review: Demographic Transition Model Can you identify what happens in each stage of the demographic transition model? Part A Drag the labels to the appropriate targets. ANSWER: True False True False True False True False Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 5 of 8 5/21/2014 8:00 PM Answer Requested Concept Review: Demographic Characteristics of Developed and Developing Nations For each demographic characteristic described in the table below, decide whether it applies to developed nations, developing nations, or neither group. Part A Drag the correct labels onto the table. Labels may be used once, more than once, or not at all. ANSWER: Concept Review: Age Structure Diagrams Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 6 of 8 5/21/2014 8:00 PM Can you label age structure diagrams? Part A Drag the labels to the appropriate targets. Pink labels indicate what each age class represents. Blue labels indicate how the population is expected to change over time. ANSWER: Correct Current Events: Nigeria Tested by Rapid Rise in Population (New York Times, 4/14/2012) Read this New York Times article and then answer the questions. Nigeria Tested by Rapid Rise in Population (4/14/2012) Registration with The New York Times provides instant access to breaking news on NYTimes.com. To register, go to http://www.nytimes.com/register. Visit http://www.nytimes.com /content/help/rights/terms/terms-of-service.html to review the current NYT Terms of Service. Part A The current human population is just over _______ billion people. ANSWER: Correct Part B How are the governments of sub-Saharan Africa reacting to a rapidly increasing population? ANSWER: Part C Which of the following tends to be true? ANSWER: 6 7 8 9 They are beginning to encourage people to have fewer children. They are doing nothing. They are waiting to hear the recommendations from the United Nations. They are still encouraging people to have many children. Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 7 of 8 5/21/2014 8:00 PM Part D You are in the Nigerian government and are working on trying to solve the problem of a rapidly increasing population. You decide to incorporate the Latin American model as part of your plan. Which of the following do you recommend? ANSWER: Part E If nearly every adult in a society is married and polygamy is common, which of the following is true? ANSWER: Part F Even if global total fertility rate drops to 2.1, estimates indicate that the human population will reach ________ by 2100. ANSWER: Score Summary: Your score on this assignment is 57.9%. You received 15.06 out of a possible total of 26 points. The relationship between changing population and unemployment rates is too variable to quantify. An increase in population leads to an increase in unemployment. Population growth and unemployment are not correlated. An increase in population leads to a decrease in unemployment. There will be tax breaks for families with fewer children. Girls will be required to finish high school. The government will impose a limit of only one child. The government will provide free family planning. There are more adult women than adult men. There are equal numbers of adult men and adult women. There are more adult men than adult women. The ratio of adult men to adult women would depend on the total fertility rate. 10 billion 12 billion 14 billion 16 billion Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 8 of 8 5/21/2014 8:00 PM

Chapter 05 Homework Due: 11:59pm on Friday, May 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Activity: Human Population Growth Click here to complete this activity. Then answer the questions. Part A Which of these was the first of the major events that stimulated an increase in the size of the human population? ANSWER: Correct The advent of agriculture is the first of the events listed here that stimulated an increase in the size of the human population. Part B Which of these was the second of the major events that stimulated an increase in the size of the human population? ANSWER: Correct The Industrial Revolution was the second of the major events that stimulated an increase in the size of the human population. Part C Which of these was the third of the major events that stimulated an increase in the size of the human population? ANSWER: Correct The advent of modern medicine is the third and most recent of the events listed here that have stimulated an increase in the population size of humans. the Industrial Revolution the advent of agriculture the discovery of antibiotics the bubonic plague the discovery of vaccines the discovery of vaccines the discovery of antibiotics the advent of agriculture the Industrial Revolution the bubonic plague the discovery of vaccines the advent of agriculture the discovery of antibiotics the discovery of vaccines and the discovery of antibiotics the Industrial Revolution Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 1 of 8 5/21/2014 8:00 PM Part D Currently, how large is the worldwide population of humans relative to Earth’s carrying capacity for humans? ANSWER: Correct Not knowing how technological innovations will affect the human population means there is insufficient information to answer this question. Activity: Analyzing Age-Structure Pyramids Click here to complete this activity. Then answer the questions. Part A Ignoring migration, the age structure of a human population likely to increase in size will have what shape? ANSWER: Correct This would mean that most individuals are in the prereproductive years. Such a population is expected to increase. Part B Ignoring migration, the age structure of a human population likely to decrease in size will have what shape? ANSWER: Correct In such a population the majority of individuals are in their postreproductive years. Such a population is expected to decrease. Part C Ignoring migration, the age structure diagram of a human population likely to maintain a relatively stable size will have what shape? There is insufficient information to answer this question. either at or above the carrying capacity below the carrying capacity above the carrying capacity at the carrying capacity Both an inverted pyramid and a rectangle tapering toward the top result in a population that increases in size. pyramid Both a pyramid and a rectangle tapering toward the top result in a population that increases in size. a rectangle tapering toward the top inverted pyramid pyramid Both an inverted pyramid and a rectangle tapering toward the top result in a population that decreases in size. Both a pyramid and a rectangle tapering toward the top result in a population that decreases in size. a rectangle tapering toward the top inverted pyramid Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 2 of 8 5/21/2014 8:00 PM ANSWER: Correct Such a population is expected to have a relatively stable size. GraphIt!: Age Pyramids and Population Growth Click here to complete the graphing activity. Then answer the questions. Part A – Question 1 The population of Greece is expected to _______. Hint 1. Review Step 2 of this activity. What shape does this population have? ANSWER: Correct Part B – Question 2 Assuming the current trend continues, in 30 years Greece will have more children than reproductive-age individuals. Hint 1. What age group will today’s newborns occupy in 2030? ANSWER: Correct Part C – Question 3 Assuming the current trend continues, in 30 years Greece will have more children than elderly members of the population. Hint 1. Both an inverted pyramid and a rectangle tapering toward the top result in a population that remains stable in size. pyramid Both a pyramid and a rectangle tapering toward the top result in a population that remains stable in size. inverted pyramid a rectangle tapering toward the top expand remain stable decline True False Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 3 of 8 5/21/2014 8:00 PM What age groups will today’s reproductive-age individuals occupy in 2030? ANSWER: Correct Part D – Question 4 Assuming the current trend continues, in 30 years Greece will have more reproductive-age individuals than children. ANSWER: Correct Part E – Question 5 Assuming the current trend continues, in 30 years Greece will have more elderly than reproductive-age individuals. ANSWER: Correct Part F – Question 6 Greece had more females than males in 2000. Which of the following is the most likely explanation for this? Hint 1. Which sex tends to live longer in the United States, males or females? ANSWER: Correct Part G – Question 7 The population of Colombia is currently _______. Hint 1. Review Step 2 of this activity. What shape does this population have? ANSWER: True False True False True False Females generally have a shorter life span than males. More females are born than males, and this difference remains throughout all age groups. There should be an equal number of males and females in every age group, so this is likely an error in the 2000 census for Greece. Males generally have a shorter life span than females. expanding stable declining Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 4 of 8 5/21/2014 8:00 PM Correct Part H – Question 8 Assuming the current trend continues, in 30 years Colombia will have more children than reproductive-age individuals. Hint 1. What age group will today’s newborns occupy in 2030? ANSWER: Correct Part I – Question 9 Assuming the current trend continues, in 30 years Colombia will have more children than elderly members of the population. Hint 1. What age groups will today’s reproductive-age individuals occupy in 2030? ANSWER: Correct Part J – Question 10 Assuming the current trend continues, in 30 years Colombia will have more reproductive-age individuals than children. ANSWER: Correct Part K – Question 11 Assuming the current trend continues, in 30 years Colombia will have more elderly than reproductive-age individuals. ANSWER: Correct Concept Review: Demographic Transition Model Can you identify what happens in each stage of the demographic transition model? Part A Drag the labels to the appropriate targets. ANSWER: True False True False True False True False Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 5 of 8 5/21/2014 8:00 PM Answer Requested Concept Review: Demographic Characteristics of Developed and Developing Nations For each demographic characteristic described in the table below, decide whether it applies to developed nations, developing nations, or neither group. Part A Drag the correct labels onto the table. Labels may be used once, more than once, or not at all. ANSWER: Concept Review: Age Structure Diagrams Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 6 of 8 5/21/2014 8:00 PM Can you label age structure diagrams? Part A Drag the labels to the appropriate targets. Pink labels indicate what each age class represents. Blue labels indicate how the population is expected to change over time. ANSWER: Correct Current Events: Nigeria Tested by Rapid Rise in Population (New York Times, 4/14/2012) Read this New York Times article and then answer the questions. Nigeria Tested by Rapid Rise in Population (4/14/2012) Registration with The New York Times provides instant access to breaking news on NYTimes.com. To register, go to http://www.nytimes.com/register. Visit http://www.nytimes.com /content/help/rights/terms/terms-of-service.html to review the current NYT Terms of Service. Part A The current human population is just over _______ billion people. ANSWER: Correct Part B How are the governments of sub-Saharan Africa reacting to a rapidly increasing population? ANSWER: Part C Which of the following tends to be true? ANSWER: 6 7 8 9 They are beginning to encourage people to have fewer children. They are doing nothing. They are waiting to hear the recommendations from the United Nations. They are still encouraging people to have many children. Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 7 of 8 5/21/2014 8:00 PM Part D You are in the Nigerian government and are working on trying to solve the problem of a rapidly increasing population. You decide to incorporate the Latin American model as part of your plan. Which of the following do you recommend? ANSWER: Part E If nearly every adult in a society is married and polygamy is common, which of the following is true? ANSWER: Part F Even if global total fertility rate drops to 2.1, estimates indicate that the human population will reach ________ by 2100. ANSWER: Score Summary: Your score on this assignment is 57.9%. You received 15.06 out of a possible total of 26 points. The relationship between changing population and unemployment rates is too variable to quantify. An increase in population leads to an increase in unemployment. Population growth and unemployment are not correlated. An increase in population leads to a decrease in unemployment. There will be tax breaks for families with fewer children. Girls will be required to finish high school. The government will impose a limit of only one child. The government will provide free family planning. There are more adult women than adult men. There are equal numbers of adult men and adult women. There are more adult men than adult women. The ratio of adult men to adult women would depend on the total fertility rate. 10 billion 12 billion 14 billion 16 billion Chapter 05 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 8 of 8 5/21/2014 8:00 PM

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A coutainor of weight W is suspended from ring A . cable BAC passes through the ring and is attached to fixed support knowing that w=376N, determine P and Q (hint The tension is the same in both postions of cables BAC.

A coutainor of weight W is suspended from ring A . cable BAC passes through the ring and is attached to fixed support knowing that w=376N, determine P and Q (hint The tension is the same in both postions of cables BAC.

 
Rationale In order to communicate in a business environment, you need to know the language. The questions below are basic concepts that all business professionals should know. Instructions Answer each of the questions below in complete sentences. At the end of the answer include the source. This does not need to be in formal MLA documentation; the URL is sufficient. Remember that plagiarism results in a 0. Do not cut and paste. Write the answers in your own words. Be prepared to discuss the answers in class. What are the differences between the board of directors and the chief executive officer (CEO)? (4 points) List and define the four functions of management. Hint: The answer is in the textbook (8 points) List and define 7 departments that would be found at a mid-size helicopter manufacturing company. (14 points) What are the difference between public relations (PR), advertising, and marketing? (6 points) List and define 3 communication concerns in the aviation industry. (6 points) List the 3 major accounting reports and what they tell about the company. (6 points) What are the differences between stock, bonds, and mutual funds? (6 points) Formatting Memo Format – Use your personal letterhead and address the memo to me. THIS IS FOR A BUSINESS COMMUNICATION CLASS

Rationale In order to communicate in a business environment, you need to know the language. The questions below are basic concepts that all business professionals should know. Instructions Answer each of the questions below in complete sentences. At the end of the answer include the source. This does not need to be in formal MLA documentation; the URL is sufficient. Remember that plagiarism results in a 0. Do not cut and paste. Write the answers in your own words. Be prepared to discuss the answers in class. What are the differences between the board of directors and the chief executive officer (CEO)? (4 points) List and define the four functions of management. Hint: The answer is in the textbook (8 points) List and define 7 departments that would be found at a mid-size helicopter manufacturing company. (14 points) What are the difference between public relations (PR), advertising, and marketing? (6 points) List and define 3 communication concerns in the aviation industry. (6 points) List the 3 major accounting reports and what they tell about the company. (6 points) What are the differences between stock, bonds, and mutual funds? (6 points) Formatting Memo Format – Use your personal letterhead and address the memo to me. THIS IS FOR A BUSINESS COMMUNICATION CLASS

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Fall Semester 2015 NMSU Econ 252, Instructor: Dr. Larry Blank Writing Assignment and Critical Thinking Problems: This assignment is worth 100 points toward your overall course average. The criteria used to grade this assignment includes the professional appearance of the document you submit, your ability to use the principles of supply and demand to critically assess the impacts, and your ability to explain your conclusions in writing. Each part can be answered in one page or less. Assigned: October 5, 2015 Deadline: Friday, October 16, 2015 You will email your assignment in Canvas. Before you email your assignment, make sure your name is on your paper AND your full name is included in the electronic file name. For example, filename: Jose Sanchez_Econ252_paper.doc I will not read your work if your name is not in the electronic filename. Assignment: Answers to all parts shall be completed in a Microsoft Word document. Begin by copying the Scenario below and then, for each part, copy the problem before completing your answer. You may want to draw your diagrams in Microsoft PowerPoint or other software and then copy and paste the diagram into the Word document as a “Picture (Enhanced Metafile)” using the “Paste Special” feature in Word. The document you turn in should be six (6) pages long. For the first page include a short title for this assignment, the course name and number, your name, and then copy and paste everything below beginning with “Scenario” onto your first page. The 2nd page of your document should include the description of Part 1 and then your diagram and answer. Do the same for Parts 2-5, with each part on a separate page. Scenario: The Federal Government implemented a policy some years ago to subsidize the production of ethanol fuel at 46 cents per gallon. See news article here: http://usnews.nbcnews.com/_news/2011/12/29/9804028-6-billion-a-year-ethanol-subsidy-dies-but-wait-theres-more?lite Ethanol is an alternative fuel (a substitute for regular gasoline) that can be used in some models of automobiles designed to burn any mix of gasoline up to 85% ethanol (fuel is known as E85, and auto manufacturers label these vehicles as “FlexFuel” and similar names). A primary input in the production of ethanol is corn. For the purposes of this assignment, assume that all relevant markets are perfectly competitive. Part 1: Show geometrically using the supply and demand curves the impact the subsidy had in the ethanol market (hint: the result has been a reduction in the market price of ethanol). Fully explain the impact of the production subsidy in terms of the behavior of producers (sellers) in the market and customers (buyers) in the market and what has happened to equilibrium price and quantity in the market for ethanol. Part 2: Show geometrically using the supply and demand curves what impact the reduction in market price for ethanol had in the market for regular gasoline. Fully explain the impact this reduced ethanol price had on the customer demand for regular gasoline. Part 3: Show geometrically using the supply and demand curves the impact due to the change in the equilibrium quantity in the market for ethanol had in the market for corn. Fully explain the impact and the resulting equilibrium price and quantity for corn. Part 4: Show geometrically using the supply and demand curves what impact the change in the market price of corn had in the market for manufactured corn tortillas (assume that the market for corn tortillas is perfectly competitive). Corn tortillas are a staple food item in the diets of millions of families across the U.S.. Fully explain the impact of change in the market price of corn in terms of the behavior of producers (sellers) in the market and customers (buyers) in the corn tortilla market. Part 5: Show geometrically using the supply and demand curves the impact in the ethanol market when the ethanol subsidy ended on Jan. 1, 2012. Give one possible explanation why I can no longer find E85 fuel at gas stations. Hint: When the subsidy still existed, the market price of E85 was about 30 cents a gallon less than regular gasoline. E85 is not a perfect substitute for regular gasoline because the performance is less and gas mileage drops by 5-7 miles per gallon.

Fall Semester 2015 NMSU Econ 252, Instructor: Dr. Larry Blank Writing Assignment and Critical Thinking Problems: This assignment is worth 100 points toward your overall course average. The criteria used to grade this assignment includes the professional appearance of the document you submit, your ability to use the principles of supply and demand to critically assess the impacts, and your ability to explain your conclusions in writing. Each part can be answered in one page or less. Assigned: October 5, 2015 Deadline: Friday, October 16, 2015 You will email your assignment in Canvas. Before you email your assignment, make sure your name is on your paper AND your full name is included in the electronic file name. For example, filename: Jose Sanchez_Econ252_paper.doc I will not read your work if your name is not in the electronic filename. Assignment: Answers to all parts shall be completed in a Microsoft Word document. Begin by copying the Scenario below and then, for each part, copy the problem before completing your answer. You may want to draw your diagrams in Microsoft PowerPoint or other software and then copy and paste the diagram into the Word document as a “Picture (Enhanced Metafile)” using the “Paste Special” feature in Word. The document you turn in should be six (6) pages long. For the first page include a short title for this assignment, the course name and number, your name, and then copy and paste everything below beginning with “Scenario” onto your first page. The 2nd page of your document should include the description of Part 1 and then your diagram and answer. Do the same for Parts 2-5, with each part on a separate page. Scenario: The Federal Government implemented a policy some years ago to subsidize the production of ethanol fuel at 46 cents per gallon. See news article here: http://usnews.nbcnews.com/_news/2011/12/29/9804028-6-billion-a-year-ethanol-subsidy-dies-but-wait-theres-more?lite Ethanol is an alternative fuel (a substitute for regular gasoline) that can be used in some models of automobiles designed to burn any mix of gasoline up to 85% ethanol (fuel is known as E85, and auto manufacturers label these vehicles as “FlexFuel” and similar names). A primary input in the production of ethanol is corn. For the purposes of this assignment, assume that all relevant markets are perfectly competitive. Part 1: Show geometrically using the supply and demand curves the impact the subsidy had in the ethanol market (hint: the result has been a reduction in the market price of ethanol). Fully explain the impact of the production subsidy in terms of the behavior of producers (sellers) in the market and customers (buyers) in the market and what has happened to equilibrium price and quantity in the market for ethanol. Part 2: Show geometrically using the supply and demand curves what impact the reduction in market price for ethanol had in the market for regular gasoline. Fully explain the impact this reduced ethanol price had on the customer demand for regular gasoline. Part 3: Show geometrically using the supply and demand curves the impact due to the change in the equilibrium quantity in the market for ethanol had in the market for corn. Fully explain the impact and the resulting equilibrium price and quantity for corn. Part 4: Show geometrically using the supply and demand curves what impact the change in the market price of corn had in the market for manufactured corn tortillas (assume that the market for corn tortillas is perfectly competitive). Corn tortillas are a staple food item in the diets of millions of families across the U.S.. Fully explain the impact of change in the market price of corn in terms of the behavior of producers (sellers) in the market and customers (buyers) in the corn tortilla market. Part 5: Show geometrically using the supply and demand curves the impact in the ethanol market when the ethanol subsidy ended on Jan. 1, 2012. Give one possible explanation why I can no longer find E85 fuel at gas stations. Hint: When the subsidy still existed, the market price of E85 was about 30 cents a gallon less than regular gasoline. E85 is not a perfect substitute for regular gasoline because the performance is less and gas mileage drops by 5-7 miles per gallon.

Assignment 9 Due: 11:59pm on Friday, April 11, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Problem 11.2 Part A Evaluate the dot product if and . Express your answer using two significant figures. ANSWER: Correct Part B Evaluate the dot product if and . Express your answer using two significant figures. ANSWER: Correct Problem 11.4  A B = 5 − 6 A i ^ j ^ = −9 − 5 B i ^ j ^ A  B  = -15  A B = −5 + 9 A i ^ j ^ = 5 + 6 B i ^ j ^ A  B  = 29 Part A What is the angle between vectors and if and ? Express your answer as an integer and include the appropriate units. ANSWER: Correct Part B What is the angle between vectors and if and ? Express your answer as an integer and include the appropriate units. ANSWER: Correct ± All Work and No Play Learning Goal: To be able to calculate work done by a constant force directed at different angles relative to displacement If an object undergoes displacement while being acted upon by a force (or several forces), it is said that work is being done on the object. If the object is moving in a straight line and the displacement and the force are known, the work done by the force can be calculated as , where is the work done by force on the object that undergoes displacement directed at angle relative to .  A B A = 2 + 5 ı ^  ^ B = −2 − 4 ı ^  ^  = 175  A B A = −6 + 2 ı ^  ^ B = − − 3 ı ^  ^  = 90 W =  = cos  F  s  F   s  W F  s  F  Note that depending on the value of , the work done can be positive, negative, or zero. In this problem, you will practice calculating work done on an object moving in a straight line. The first series of questions is related to the accompanying figure. Part A What can be said about the sign of the work done by the force ? ANSWER: Correct When , the cosine of is zero, and therefore the work done is zero. Part B cos  F  1 It is positive. It is negative. It is zero. There is not enough information to answer the question.  = 90  What can be said about the work done by force ? ANSWER: Correct When , is positive, and so the work done is positive. Part C The work done by force is ANSWER: Correct When , is negative, and so the work done is negative. Part D The work done by force is ANSWER: F  2 It is positive. It is negative. It is zero. 0 <  < 90 cos  F  3 positive negative zero 90 <  < 180 cos  F  4 Correct Part E The work done by force is ANSWER: Correct positive negative zero F  5 positive negative zero Part F The work done by force is ANSWER: Correct Part G The work done by force is ANSWER: Correct In the next series of questions, you will use the formula to calculate the work done by various forces on an object that moves 160 meters to the right. F  6 positive negative zero F  7 positive negative zero W =  = cos  F  s  F   s  Part H Find the work done by the 18-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: Correct Part I Find the work done by the 30-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: Correct Part J Find the work done by the 12-newton force. Use two significant figures in your answer. Express your answer in joules. W W = 2900 J W W = 4200 J W ANSWER: Correct Part K Find the work done by the 15-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: Correct Introduction to Potential Energy Learning Goal: Understand that conservative forces can be removed from the work integral by incorporating them into a new form of energy called potential energy that must be added to the kinetic energy to get the total mechanical energy. The first part of this problem contains short-answer questions that review the work-energy theorem. In the second part we introduce the concept of potential energy. But for now, please answer in terms of the work-energy theorem. Work-Energy Theorem The work-energy theorem states , where is the work done by all forces that act on the object, and and are the initial and final kinetic energies, respectively. Part A The work-energy theorem states that a force acting on a particle as it moves over a ______ changes the ______ energy of the particle if the force has a component parallel to the motion. W = -1900 J W W = -1800 J Kf = Ki + Wall Wall Ki Kf Choose the best answer to fill in the blanks above: ANSWER: Correct It is important that the force have a component acting in the direction of motion. For example, if a ball is attached to a string and whirled in uniform circular motion, the string does apply a force to the ball, but since the string's force is always perpendicular to the motion it does no work and cannot change the kinetic energy of the ball. Part B To calculate the change in energy, you must know the force as a function of _______. The work done by the force causes the energy change. Choose the best answer to fill in the blank above: ANSWER: Correct Part C To illustrate the work-energy concept, consider the case of a stone falling from to under the influence of gravity. Using the work-energy concept, we say that work is done by the gravitational _____, resulting in an increase of the ______ energy of the stone. Choose the best answer to fill in the blanks above: distance / potential distance / kinetic vertical displacement / potential none of the above acceleration work distance potential energy xi xf ANSWER: Correct Potential Energy You should read about potential energy in your text before answering the following questions. Potential energy is a concept that builds on the work-energy theorem, enlarging the concept of energy in the most physically useful way. The key aspect that allows for potential energy is the existence of conservative forces, forces for which the work done on an object does not depend on the path of the object, only the initial and final positions of the object. The gravitational force is conservative; the frictional force is not. The change in potential energy is the negative of the work done by conservative forces. Hence considering the initial and final potential energies is equivalent to calculating the work done by the conservative forces. When potential energy is used, it replaces the work done by the associated conservative force. Then only the work due to nonconservative forces needs to be calculated. In summary, when using the concept of potential energy, only nonconservative forces contribute to the work, which now changes the total energy: , where and are the final and initial potential energies, and is the work due only to nonconservative forces. Now, we will revisit the falling stone example using the concept of potential energy. Part D Rather than ascribing the increased kinetic energy of the stone to the work of gravity, we now (when using potential energy rather than work-energy) say that the increased kinetic energy comes from the ______ of the _______ energy. Choose the best answer to fill in the blanks above: ANSWER: force / kinetic potential energy / potential force / potential potential energy / kinetic Kf + Uf = Ef = Wnc + Ei = Wnc + Ki + Ui Uf Ui Wnc Correct Part E This process happens in such a way that total mechanical energy, equal to the ______ of the kinetic and potential energies, is _______. Choose the best answer to fill in the blanks above: ANSWER: Correct Problem 11.7 Part A How much work is done by the force 2.2 6.6 on a particle that moves through displacement 3.9 Express your answer to two significant figures and include the appropriate units. ANSWER: work / potential force / kinetic change / potential sum / conserved sum / zero sum / not conserved difference / conserved F  = (− + i ^ ) N j ^ ! = r m i ^ Correct Part B How much work is done by the force 2.2 6.6 on a particle that moves through displacement 3.9 Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.10 A 1.8 book is lying on a 0.80- -high table. You pick it up and place it on a bookshelf 2.27 above the floor. Part A How much work does gravity do on the book? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B W = -8.6 J F  = (− + i ^ ) N j ^ ! = r m? j ^ W = 26 J kg m m Wg = -26 J How much work does your hand do on the book? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.12 The three ropes shown in the bird's-eye view of the figure are used to drag a crate 3.3 across the floor. Part A How much work is done by each of the three forces? Express your answers using two significant figures. Enter your answers numerically separated by commas. ANSWER: WH = 26 J m W1 , W2 , W3 = 1.9,1.2,-2.1 kJ Correct Enhanced EOC: Problem 11.16 A 1.2 particle moving along the x-axis experiences the force shown in the figure. The particle's velocity is 4.6 at . You may want to review ( pages 286 - 287) . For help with math skills, you may want to review: The Definite Integral Part A What is its velocity at ? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem What is the work–kinetic energy theorem? What is the kinetic energy at ? How is the work done in going from to related to force shown in the graph? Using the work–kinetic energy theorem, what is the kinetic energy at ? What is the velocity at ? ANSWER: kg m/s x = 0m x = 2m x = 0 m x = 0 m x = 2 m x = 2 m x = 2 m Correct Part B What is its velocity at ? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem What is the work–kinetic energy theorem? What is the kinetic energy at ? How is the work done in going from to related to force shown in the graph? Can the work be negative? Using the work–kinetic energy theorem, what is the kinetic energy at ? What is the velocity at ? ANSWER: Correct Work on a Sliding Block A block of weight sits on a frictionless inclined plane, which makes an angle with respect to the horizontal, as shown. A force of magnitude , applied parallel to the incline, pulls the block up the plane at constant speed. v = 6.2 ms x = 4m x = 0 m x = 0 m x = 4 m x = 4 m x = 4 m v = 4.6 ms w  F Part A The block moves a distance up the incline. The block does not stop after moving this distance but continues to move with constant speed. What is the total work done on the block by all forces? (Include only the work done after the block has started moving, not the work needed to start the block moving from rest.) Express your answer in terms of given quantities. Hint 1. What physical principle to use To find the total work done on the block, use the work-energy theorem: . Hint 2. Find the change in kinetic energy What is the change in the kinetic energy of the block, from the moment it starts moving until it has been pulled a distance ? Remember that the block is pulled at constant speed. Hint 1. Consider kinetic energy If the block's speed does not change, its kinetic energy cannot change. ANSWER: ANSWER: L Wtot Wtot = Kf − Ki L Kf − Ki = 0 Wtot = 0 Correct Part B What is , the work done on the block by the force of gravity as the block moves a distance up the incline? Express the work done by gravity in terms of the weight and any other quantities given in the problem introduction. Hint 1. Force diagram Hint 2. Force of gravity component What is the component of the force of gravity in the direction of the block's displacement (along the inclined plane)? Express your answer in terms of and . Hint 1. Relative direction of the force and the motion Remember that the force of gravity acts down the plane, whereas the block's displacement is directed up the plane. ANSWER: Wg L w w  ANSWER: Correct Part C What is , the work done on the block by the applied force as the block moves a distance up the incline? Express your answer in terms of and other given quantities. Hint 1. How to find the work done by a constant force Remember that the work done on an object by a particular force is the integral of the dot product of the force and the instantaneous displacement of the object, over the path followed by the object. In this case, since the force is constant and the path is a straight segment of length up the inclined plane, the dot product becomes simple multiplication. ANSWER: Correct Part D What is , the work done on the block by the normal force as the block moves a distance up the inclined plane? Express your answer in terms of given quantities. Hint 1. First step in computing the work Fg|| = −wsin() Wg = −wLsin() WF F L F L WF = FL Wnormal L The work done by the normal force is equal to the dot product of the force vector and the block's displacement vector. The normal force and the block's displacement vector are perpendicular. Therefore, what is their dot product? ANSWER: ANSWER: Correct Problem 11.20 A particle moving along the -axis has the potential energy , where is in . Part A What is the -component of the force on the particle at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the -component of the force on the particle at ? Express your answer to two significant figures and include the appropriate units. N  L = 0 Wnormal = 0 y U = 3.2y3 J y m y y = 0 m Fy = 0 N y y = 1 m ANSWER: Correct Part C What is the -component of the force on the particle at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.28 A cable with 25.0 of tension pulls straight up on a 1.08 block that is initially at rest. Part A What is the block's speed after being lifted 2.40 ? Solve this problem using work and energy. Express your answer with the appropriate units. ANSWER: Correct Fy = -9.6 N y y = 2 m Fy = -38 N N kg m vf = 8.00 ms Problem 11.29 Part A How much work does an elevator motor do to lift a 1500 elevator a height of 110 ? Express your answer with the appropriate units. ANSWER: Correct Part B How much power must the motor supply to do this in 50 at constant speed? Express your answer with the appropriate units. ANSWER: Correct Problem 11.32 How many energy is consumed by a 1.20 hair dryer used for 10.0 and a 11.0 night light left on for 16.0 ? Part A Hair dryer: Express your answer with the appropriate units. kg m Wext = 1.62×106 J s = 3.23×104 P W kW min W hr ANSWER: Correct Part B Night light: Express your answer with the appropriate units. ANSWER: Correct Problem 11.42 A 2500 elevator accelerates upward at 1.20 for 10.0 , starting from rest. Part A How much work does gravity do on the elevator? Express your answer with the appropriate units. ANSWER: Correct W = 7.20×105 J = 6.34×105 W J kg m/s2 m −2.45×105 J Part B How much work does the tension in the elevator cable do on the elevator? Express your answer with the appropriate units. ANSWER: Correct Part C Use the work-kinetic energy theorem to find the kinetic energy of the elevator as it reaches 10.0 . Express your answer with the appropriate units. ANSWER: Correct Part D What is the speed of the elevator as it reaches 10.0 ? Express your answer with the appropriate units. ANSWER: Correct 2.75×105 J m 3.00×104 J m 4.90 ms Problem 11.47 A horizontal spring with spring constant 130 is compressed 17 and used to launch a 2.4 box across a frictionless, horizontal surface. After the box travels some distance, the surface becomes rough. The coefficient of kinetic friction of the box on the surface is 0.15. Part A Use work and energy to find how far the box slides across the rough surface before stopping. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.49 Truck brakes can fail if they get too hot. In some mountainous areas, ramps of loose gravel are constructed to stop runaway trucks that have lost their brakes. The combination of a slight upward slope and a large coefficient of rolling friction as the truck tires sink into the gravel brings the truck safely to a halt. Suppose a gravel ramp slopes upward at 6.0 and the coefficient of rolling friction is 0.45. Part A Use work and energy to find the length of a ramp that will stop a 15,000 truck that enters the ramp at 30 . Express your answer to two significant figures and include the appropriate units. ANSWER: Correct N/m cm kg l = 53 cm kg m/s l = 83 m Problem 11.51 Use work and energy to find an expression for the speed of the block in the following figure just before it hits the floor. Part A Find an expression for the speed of the block if the coefficient of kinetic friction for the block on the table is . Express your answer in terms of the variables , , , , and free fall acceleration . ANSWER: Part B Find an expression for the speed of the block if the table is frictionless. Express your answer in terms of the variables , , , and free fall acceleration . ANSWER: μk M m h μk g v = M m h g Problem 11.57 The spring shown in the figure is compressed 60 and used to launch a 100 physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the incline is 0.12 . Part A What is the student's speed just after losing contact with the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How far up the incline does the student go? Express your answer to two significant figures and include the appropriate units. ANSWER: v = cm kg 30 v = 17 ms Correct Score Summary: Your score on this assignment is 93.6%. You received 112.37 out of a possible total of 120 points. !s = 41 m

Assignment 9 Due: 11:59pm on Friday, April 11, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Problem 11.2 Part A Evaluate the dot product if and . Express your answer using two significant figures. ANSWER: Correct Part B Evaluate the dot product if and . Express your answer using two significant figures. ANSWER: Correct Problem 11.4  A B = 5 − 6 A i ^ j ^ = −9 − 5 B i ^ j ^ A  B  = -15  A B = −5 + 9 A i ^ j ^ = 5 + 6 B i ^ j ^ A  B  = 29 Part A What is the angle between vectors and if and ? Express your answer as an integer and include the appropriate units. ANSWER: Correct Part B What is the angle between vectors and if and ? Express your answer as an integer and include the appropriate units. ANSWER: Correct ± All Work and No Play Learning Goal: To be able to calculate work done by a constant force directed at different angles relative to displacement If an object undergoes displacement while being acted upon by a force (or several forces), it is said that work is being done on the object. If the object is moving in a straight line and the displacement and the force are known, the work done by the force can be calculated as , where is the work done by force on the object that undergoes displacement directed at angle relative to .  A B A = 2 + 5 ı ^  ^ B = −2 − 4 ı ^  ^  = 175  A B A = −6 + 2 ı ^  ^ B = − − 3 ı ^  ^  = 90 W =  = cos  F  s  F   s  W F  s  F  Note that depending on the value of , the work done can be positive, negative, or zero. In this problem, you will practice calculating work done on an object moving in a straight line. The first series of questions is related to the accompanying figure. Part A What can be said about the sign of the work done by the force ? ANSWER: Correct When , the cosine of is zero, and therefore the work done is zero. Part B cos  F  1 It is positive. It is negative. It is zero. There is not enough information to answer the question.  = 90  What can be said about the work done by force ? ANSWER: Correct When , is positive, and so the work done is positive. Part C The work done by force is ANSWER: Correct When , is negative, and so the work done is negative. Part D The work done by force is ANSWER: F  2 It is positive. It is negative. It is zero. 0 <  < 90 cos  F  3 positive negative zero 90 <  < 180 cos  F  4 Correct Part E The work done by force is ANSWER: Correct positive negative zero F  5 positive negative zero Part F The work done by force is ANSWER: Correct Part G The work done by force is ANSWER: Correct In the next series of questions, you will use the formula to calculate the work done by various forces on an object that moves 160 meters to the right. F  6 positive negative zero F  7 positive negative zero W =  = cos  F  s  F   s  Part H Find the work done by the 18-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: Correct Part I Find the work done by the 30-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: Correct Part J Find the work done by the 12-newton force. Use two significant figures in your answer. Express your answer in joules. W W = 2900 J W W = 4200 J W ANSWER: Correct Part K Find the work done by the 15-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: Correct Introduction to Potential Energy Learning Goal: Understand that conservative forces can be removed from the work integral by incorporating them into a new form of energy called potential energy that must be added to the kinetic energy to get the total mechanical energy. The first part of this problem contains short-answer questions that review the work-energy theorem. In the second part we introduce the concept of potential energy. But for now, please answer in terms of the work-energy theorem. Work-Energy Theorem The work-energy theorem states , where is the work done by all forces that act on the object, and and are the initial and final kinetic energies, respectively. Part A The work-energy theorem states that a force acting on a particle as it moves over a ______ changes the ______ energy of the particle if the force has a component parallel to the motion. W = -1900 J W W = -1800 J Kf = Ki + Wall Wall Ki Kf Choose the best answer to fill in the blanks above: ANSWER: Correct It is important that the force have a component acting in the direction of motion. For example, if a ball is attached to a string and whirled in uniform circular motion, the string does apply a force to the ball, but since the string's force is always perpendicular to the motion it does no work and cannot change the kinetic energy of the ball. Part B To calculate the change in energy, you must know the force as a function of _______. The work done by the force causes the energy change. Choose the best answer to fill in the blank above: ANSWER: Correct Part C To illustrate the work-energy concept, consider the case of a stone falling from to under the influence of gravity. Using the work-energy concept, we say that work is done by the gravitational _____, resulting in an increase of the ______ energy of the stone. Choose the best answer to fill in the blanks above: distance / potential distance / kinetic vertical displacement / potential none of the above acceleration work distance potential energy xi xf ANSWER: Correct Potential Energy You should read about potential energy in your text before answering the following questions. Potential energy is a concept that builds on the work-energy theorem, enlarging the concept of energy in the most physically useful way. The key aspect that allows for potential energy is the existence of conservative forces, forces for which the work done on an object does not depend on the path of the object, only the initial and final positions of the object. The gravitational force is conservative; the frictional force is not. The change in potential energy is the negative of the work done by conservative forces. Hence considering the initial and final potential energies is equivalent to calculating the work done by the conservative forces. When potential energy is used, it replaces the work done by the associated conservative force. Then only the work due to nonconservative forces needs to be calculated. In summary, when using the concept of potential energy, only nonconservative forces contribute to the work, which now changes the total energy: , where and are the final and initial potential energies, and is the work due only to nonconservative forces. Now, we will revisit the falling stone example using the concept of potential energy. Part D Rather than ascribing the increased kinetic energy of the stone to the work of gravity, we now (when using potential energy rather than work-energy) say that the increased kinetic energy comes from the ______ of the _______ energy. Choose the best answer to fill in the blanks above: ANSWER: force / kinetic potential energy / potential force / potential potential energy / kinetic Kf + Uf = Ef = Wnc + Ei = Wnc + Ki + Ui Uf Ui Wnc Correct Part E This process happens in such a way that total mechanical energy, equal to the ______ of the kinetic and potential energies, is _______. Choose the best answer to fill in the blanks above: ANSWER: Correct Problem 11.7 Part A How much work is done by the force 2.2 6.6 on a particle that moves through displacement 3.9 Express your answer to two significant figures and include the appropriate units. ANSWER: work / potential force / kinetic change / potential sum / conserved sum / zero sum / not conserved difference / conserved F  = (− + i ^ ) N j ^ ! = r m i ^ Correct Part B How much work is done by the force 2.2 6.6 on a particle that moves through displacement 3.9 Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.10 A 1.8 book is lying on a 0.80- -high table. You pick it up and place it on a bookshelf 2.27 above the floor. Part A How much work does gravity do on the book? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B W = -8.6 J F  = (− + i ^ ) N j ^ ! = r m? j ^ W = 26 J kg m m Wg = -26 J How much work does your hand do on the book? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.12 The three ropes shown in the bird's-eye view of the figure are used to drag a crate 3.3 across the floor. Part A How much work is done by each of the three forces? Express your answers using two significant figures. Enter your answers numerically separated by commas. ANSWER: WH = 26 J m W1 , W2 , W3 = 1.9,1.2,-2.1 kJ Correct Enhanced EOC: Problem 11.16 A 1.2 particle moving along the x-axis experiences the force shown in the figure. The particle's velocity is 4.6 at . You may want to review ( pages 286 - 287) . For help with math skills, you may want to review: The Definite Integral Part A What is its velocity at ? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem What is the work–kinetic energy theorem? What is the kinetic energy at ? How is the work done in going from to related to force shown in the graph? Using the work–kinetic energy theorem, what is the kinetic energy at ? What is the velocity at ? ANSWER: kg m/s x = 0m x = 2m x = 0 m x = 0 m x = 2 m x = 2 m x = 2 m Correct Part B What is its velocity at ? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem What is the work–kinetic energy theorem? What is the kinetic energy at ? How is the work done in going from to related to force shown in the graph? Can the work be negative? Using the work–kinetic energy theorem, what is the kinetic energy at ? What is the velocity at ? ANSWER: Correct Work on a Sliding Block A block of weight sits on a frictionless inclined plane, which makes an angle with respect to the horizontal, as shown. A force of magnitude , applied parallel to the incline, pulls the block up the plane at constant speed. v = 6.2 ms x = 4m x = 0 m x = 0 m x = 4 m x = 4 m x = 4 m v = 4.6 ms w  F Part A The block moves a distance up the incline. The block does not stop after moving this distance but continues to move with constant speed. What is the total work done on the block by all forces? (Include only the work done after the block has started moving, not the work needed to start the block moving from rest.) Express your answer in terms of given quantities. Hint 1. What physical principle to use To find the total work done on the block, use the work-energy theorem: . Hint 2. Find the change in kinetic energy What is the change in the kinetic energy of the block, from the moment it starts moving until it has been pulled a distance ? Remember that the block is pulled at constant speed. Hint 1. Consider kinetic energy If the block's speed does not change, its kinetic energy cannot change. ANSWER: ANSWER: L Wtot Wtot = Kf − Ki L Kf − Ki = 0 Wtot = 0 Correct Part B What is , the work done on the block by the force of gravity as the block moves a distance up the incline? Express the work done by gravity in terms of the weight and any other quantities given in the problem introduction. Hint 1. Force diagram Hint 2. Force of gravity component What is the component of the force of gravity in the direction of the block's displacement (along the inclined plane)? Express your answer in terms of and . Hint 1. Relative direction of the force and the motion Remember that the force of gravity acts down the plane, whereas the block's displacement is directed up the plane. ANSWER: Wg L w w  ANSWER: Correct Part C What is , the work done on the block by the applied force as the block moves a distance up the incline? Express your answer in terms of and other given quantities. Hint 1. How to find the work done by a constant force Remember that the work done on an object by a particular force is the integral of the dot product of the force and the instantaneous displacement of the object, over the path followed by the object. In this case, since the force is constant and the path is a straight segment of length up the inclined plane, the dot product becomes simple multiplication. ANSWER: Correct Part D What is , the work done on the block by the normal force as the block moves a distance up the inclined plane? Express your answer in terms of given quantities. Hint 1. First step in computing the work Fg|| = −wsin() Wg = −wLsin() WF F L F L WF = FL Wnormal L The work done by the normal force is equal to the dot product of the force vector and the block's displacement vector. The normal force and the block's displacement vector are perpendicular. Therefore, what is their dot product? ANSWER: ANSWER: Correct Problem 11.20 A particle moving along the -axis has the potential energy , where is in . Part A What is the -component of the force on the particle at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the -component of the force on the particle at ? Express your answer to two significant figures and include the appropriate units. N  L = 0 Wnormal = 0 y U = 3.2y3 J y m y y = 0 m Fy = 0 N y y = 1 m ANSWER: Correct Part C What is the -component of the force on the particle at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.28 A cable with 25.0 of tension pulls straight up on a 1.08 block that is initially at rest. Part A What is the block's speed after being lifted 2.40 ? Solve this problem using work and energy. Express your answer with the appropriate units. ANSWER: Correct Fy = -9.6 N y y = 2 m Fy = -38 N N kg m vf = 8.00 ms Problem 11.29 Part A How much work does an elevator motor do to lift a 1500 elevator a height of 110 ? Express your answer with the appropriate units. ANSWER: Correct Part B How much power must the motor supply to do this in 50 at constant speed? Express your answer with the appropriate units. ANSWER: Correct Problem 11.32 How many energy is consumed by a 1.20 hair dryer used for 10.0 and a 11.0 night light left on for 16.0 ? Part A Hair dryer: Express your answer with the appropriate units. kg m Wext = 1.62×106 J s = 3.23×104 P W kW min W hr ANSWER: Correct Part B Night light: Express your answer with the appropriate units. ANSWER: Correct Problem 11.42 A 2500 elevator accelerates upward at 1.20 for 10.0 , starting from rest. Part A How much work does gravity do on the elevator? Express your answer with the appropriate units. ANSWER: Correct W = 7.20×105 J = 6.34×105 W J kg m/s2 m −2.45×105 J Part B How much work does the tension in the elevator cable do on the elevator? Express your answer with the appropriate units. ANSWER: Correct Part C Use the work-kinetic energy theorem to find the kinetic energy of the elevator as it reaches 10.0 . Express your answer with the appropriate units. ANSWER: Correct Part D What is the speed of the elevator as it reaches 10.0 ? Express your answer with the appropriate units. ANSWER: Correct 2.75×105 J m 3.00×104 J m 4.90 ms Problem 11.47 A horizontal spring with spring constant 130 is compressed 17 and used to launch a 2.4 box across a frictionless, horizontal surface. After the box travels some distance, the surface becomes rough. The coefficient of kinetic friction of the box on the surface is 0.15. Part A Use work and energy to find how far the box slides across the rough surface before stopping. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 11.49 Truck brakes can fail if they get too hot. In some mountainous areas, ramps of loose gravel are constructed to stop runaway trucks that have lost their brakes. The combination of a slight upward slope and a large coefficient of rolling friction as the truck tires sink into the gravel brings the truck safely to a halt. Suppose a gravel ramp slopes upward at 6.0 and the coefficient of rolling friction is 0.45. Part A Use work and energy to find the length of a ramp that will stop a 15,000 truck that enters the ramp at 30 . Express your answer to two significant figures and include the appropriate units. ANSWER: Correct N/m cm kg l = 53 cm kg m/s l = 83 m Problem 11.51 Use work and energy to find an expression for the speed of the block in the following figure just before it hits the floor. Part A Find an expression for the speed of the block if the coefficient of kinetic friction for the block on the table is . Express your answer in terms of the variables , , , , and free fall acceleration . ANSWER: Part B Find an expression for the speed of the block if the table is frictionless. Express your answer in terms of the variables , , , and free fall acceleration . ANSWER: μk M m h μk g v = M m h g Problem 11.57 The spring shown in the figure is compressed 60 and used to launch a 100 physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the incline is 0.12 . Part A What is the student's speed just after losing contact with the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How far up the incline does the student go? Express your answer to two significant figures and include the appropriate units. ANSWER: v = cm kg 30 v = 17 ms Correct Score Summary: Your score on this assignment is 93.6%. You received 112.37 out of a possible total of 120 points. !s = 41 m

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Chapter 07 Homework Due: 11:59pm on Friday, May 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy BioFlix Quiz: The Carbon Cycle Watch the animation at left before answering the questions below. Part A An organism gets carbon by using carbon dioxide in the atmosphere to make sugar molecules. This organism is a Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: Correct During photosynthesis, producers use carbon dioxide to make sugar molecules. Part B Which organisms play a role in returning carbon to the atmosphere? Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: higher-level consumer. producer. primary consumer. decomposer. None of the above Consumers and decomposers, but not producers. Producers only. Decomposers only. Consumers only. Producers, consumers, and decomposers. Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 1 of 7 5/21/2014 8:02 PM Correct Producers, consumers, and decomposers all return carbon dioxide to the atmosphere during cellular respiration. Part C Every carbon atom in the organic molecules that make up your body MUST recently have been part of Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: Correct You are a consumer, and all your carbon comes ultimately from plants and other producers. Part D Imagine following a single carbon atom through the carbon cycle. Which of the following is a possible path for the carbon atom to take? Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: Correct Carbon moves from the atmosphere into a producer (such as a plant), up the food chain, and then back to the atmosphere during cellular respiration. Part E Which process or processes return carbon to the atmosphere? Hint 1. Review the animation. ANSWER: Correct Cellular respiration results in the release of carbon dioxide to the atmosphere. a higher-level consumer. a primary consumer. a decomposer. a producer. a sugar molecule made in one of your chloroplasts. The atmosphere; a plant; a higher-level consumer; then back to the atmosphere. The atmosphere; a plant; an herbivore; another plant; then back to the atmosphere. The atmosphere, a plant, a herbivore, a decomposer, then back to the atmosphere The atmosphere; a decomposer; a higher-level consumer; then back to the atmosphere. The atmosphere; a decomposer; then back to the atmosphere. Cellular respiration only Photosynthesis only Cellular respiration and photosynthesis Breakdown of large organic molecules into smaller organic molecules Cellular respiration and the breakdown of large organic molecules into smaller organic molecules Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 2 of 7 5/21/2014 8:02 PM Activity: The Nitrogen Cycle Click here to complete this activity. Then answer the questions. Part A Nitrifying bacteria convert _____ to _____. ANSWER: Correct Nitrifying bacteria convert ammonium to nitrites. Part B _____ removes nitrogen from the atmosphere. ANSWER: Correct Nitrogen fixation is the conversion of nitrogen gas to a form that can be used by plants (and other organisms). Part C Assimilation is indicated by the letter(s) _____. nitrogen gas … ammonium nitrogen gas … nitrates ammonium … nitrites nitrates … nitrogen gas ammonium … nitrogen gas Denitrification Nitrification Mineralization Nitrogen fixation Assimilation Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 3 of 7 5/21/2014 8:02 PM ANSWER: Correct Assimilation is the uptake of nutrients into an organism. Part D Nitrogen-fixing bacteria is(are) indicated by the letter(s) _____. ANSWER: Correct Both of these pointers are indicating nitrogen-fixing bacteria. Nitrogen fixation is the conversion of nitrogen to a form that plants can use. Part E Nitrification is indicated by the letter(s) _____. ANSWER: C B A D and E C and D B and C A and B D and E C and D A Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 4 of 7 5/21/2014 8:02 PM Correct Nitrification is the conversion of organic nitrogen-containing compounds to nitrites and nitrates. Part F Denitrifying bacteria convert _____ to _____. ANSWER: Correct Denitrifying bacteria convert nitrates to nitrogen gas. Part G Which one of these is a nitrate? ANSWER: Correct NO3 – is a nitrate. Part H Which one of these is a nitrite? ANSWER: Correct This is a nitrite. GeoScience: Earth’s Water and the Hydrologic Cycle A B B and C D and E B and E nitrogen gas … nitrites nitrogen gas … ammonium nitrates … nitrogen gas ammonium … nitrogen gas nitrogen gas … nitrates NO2 – NH4 – NH2 SH NO3 – PO4 – NH2 NH4 – NO2 – NO3 – Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 5 of 7 5/21/2014 8:02 PM When you have finished, answer the questions. Part A The largest percentage of fresh water today is located in: ANSWER: Correct Ice sheets and glaciers are the greatest single repository of fresh water: they contain 77.3% of all Earth’s fresh water and 99.357% of all Earth’s surface fresh water. Part B Earth’s oceans hold: ANSWER: Correct The oceans contain 97.22% of all water, comprising about 1.321 billion cubic kilometers of salt water. This leaves only 2.78% of all of Earth’s water as fresh water (non-oceanic). Part C Which of the following is true of the hydrologic cycle? ANSWER: Correct About 20% of the moisture evaporated from the ocean combines with 2% of land-derived moisture to produce 22% of all precipitation that falls over land. Clearly, the bulk of continental precipitation comes from the oceanic portion of the cycle. Concept Review: Eutrophication Can you sequence the steps in the eutrophication process that occurs in a body of water? Part A Drag each statement to the appropriate location in the flowchart of the eutrophication process. ANSWER: soil. ice sheets and glaciers. the rivers and lakes of the world. groundwater resources. about the same amount of water as all groundwater sources combined. most of the fresh water on Earth. the bulk of all of the water found on Earth. about the same amount of water as all Earth’s rivers and lakes combined. Atmospheric water and surface water do not mix. Most evaporation on Earth occurs over the continents. The bulk of the precipitation occurs over land. Most of the water that falls on the continents is derived from the oceans. Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 6 of 7 5/21/2014 8:02 PM Concept Review: Biogeochemical Cycles Can you sort the items by which biogeochemical cycle they apply to? Part A Drag each description to the appropriate bin. ANSWER: Score Summary: Your score on this assignment is 62.3%. You received 12.45 out of a possible total of 20 points. Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 7 of 7 5/21/2014 8:02 PM

Chapter 07 Homework Due: 11:59pm on Friday, May 23, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy BioFlix Quiz: The Carbon Cycle Watch the animation at left before answering the questions below. Part A An organism gets carbon by using carbon dioxide in the atmosphere to make sugar molecules. This organism is a Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: Correct During photosynthesis, producers use carbon dioxide to make sugar molecules. Part B Which organisms play a role in returning carbon to the atmosphere? Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: higher-level consumer. producer. primary consumer. decomposer. None of the above Consumers and decomposers, but not producers. Producers only. Decomposers only. Consumers only. Producers, consumers, and decomposers. Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 1 of 7 5/21/2014 8:02 PM Correct Producers, consumers, and decomposers all return carbon dioxide to the atmosphere during cellular respiration. Part C Every carbon atom in the organic molecules that make up your body MUST recently have been part of Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: Correct You are a consumer, and all your carbon comes ultimately from plants and other producers. Part D Imagine following a single carbon atom through the carbon cycle. Which of the following is a possible path for the carbon atom to take? Hint 1. Review the animation or your Study Sheet for The Carbon Cycle. ANSWER: Correct Carbon moves from the atmosphere into a producer (such as a plant), up the food chain, and then back to the atmosphere during cellular respiration. Part E Which process or processes return carbon to the atmosphere? Hint 1. Review the animation. ANSWER: Correct Cellular respiration results in the release of carbon dioxide to the atmosphere. a higher-level consumer. a primary consumer. a decomposer. a producer. a sugar molecule made in one of your chloroplasts. The atmosphere; a plant; a higher-level consumer; then back to the atmosphere. The atmosphere; a plant; an herbivore; another plant; then back to the atmosphere. The atmosphere, a plant, a herbivore, a decomposer, then back to the atmosphere The atmosphere; a decomposer; a higher-level consumer; then back to the atmosphere. The atmosphere; a decomposer; then back to the atmosphere. Cellular respiration only Photosynthesis only Cellular respiration and photosynthesis Breakdown of large organic molecules into smaller organic molecules Cellular respiration and the breakdown of large organic molecules into smaller organic molecules Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 2 of 7 5/21/2014 8:02 PM Activity: The Nitrogen Cycle Click here to complete this activity. Then answer the questions. Part A Nitrifying bacteria convert _____ to _____. ANSWER: Correct Nitrifying bacteria convert ammonium to nitrites. Part B _____ removes nitrogen from the atmosphere. ANSWER: Correct Nitrogen fixation is the conversion of nitrogen gas to a form that can be used by plants (and other organisms). Part C Assimilation is indicated by the letter(s) _____. nitrogen gas … ammonium nitrogen gas … nitrates ammonium … nitrites nitrates … nitrogen gas ammonium … nitrogen gas Denitrification Nitrification Mineralization Nitrogen fixation Assimilation Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 3 of 7 5/21/2014 8:02 PM ANSWER: Correct Assimilation is the uptake of nutrients into an organism. Part D Nitrogen-fixing bacteria is(are) indicated by the letter(s) _____. ANSWER: Correct Both of these pointers are indicating nitrogen-fixing bacteria. Nitrogen fixation is the conversion of nitrogen to a form that plants can use. Part E Nitrification is indicated by the letter(s) _____. ANSWER: C B A D and E C and D B and C A and B D and E C and D A Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 4 of 7 5/21/2014 8:02 PM Correct Nitrification is the conversion of organic nitrogen-containing compounds to nitrites and nitrates. Part F Denitrifying bacteria convert _____ to _____. ANSWER: Correct Denitrifying bacteria convert nitrates to nitrogen gas. Part G Which one of these is a nitrate? ANSWER: Correct NO3 – is a nitrate. Part H Which one of these is a nitrite? ANSWER: Correct This is a nitrite. GeoScience: Earth’s Water and the Hydrologic Cycle A B B and C D and E B and E nitrogen gas … nitrites nitrogen gas … ammonium nitrates … nitrogen gas ammonium … nitrogen gas nitrogen gas … nitrates NO2 – NH4 – NH2 SH NO3 – PO4 – NH2 NH4 – NO2 – NO3 – Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 5 of 7 5/21/2014 8:02 PM When you have finished, answer the questions. Part A The largest percentage of fresh water today is located in: ANSWER: Correct Ice sheets and glaciers are the greatest single repository of fresh water: they contain 77.3% of all Earth’s fresh water and 99.357% of all Earth’s surface fresh water. Part B Earth’s oceans hold: ANSWER: Correct The oceans contain 97.22% of all water, comprising about 1.321 billion cubic kilometers of salt water. This leaves only 2.78% of all of Earth’s water as fresh water (non-oceanic). Part C Which of the following is true of the hydrologic cycle? ANSWER: Correct About 20% of the moisture evaporated from the ocean combines with 2% of land-derived moisture to produce 22% of all precipitation that falls over land. Clearly, the bulk of continental precipitation comes from the oceanic portion of the cycle. Concept Review: Eutrophication Can you sequence the steps in the eutrophication process that occurs in a body of water? Part A Drag each statement to the appropriate location in the flowchart of the eutrophication process. ANSWER: soil. ice sheets and glaciers. the rivers and lakes of the world. groundwater resources. about the same amount of water as all groundwater sources combined. most of the fresh water on Earth. the bulk of all of the water found on Earth. about the same amount of water as all Earth’s rivers and lakes combined. Atmospheric water and surface water do not mix. Most evaporation on Earth occurs over the continents. The bulk of the precipitation occurs over land. Most of the water that falls on the continents is derived from the oceans. Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 6 of 7 5/21/2014 8:02 PM Concept Review: Biogeochemical Cycles Can you sort the items by which biogeochemical cycle they apply to? Part A Drag each description to the appropriate bin. ANSWER: Score Summary: Your score on this assignment is 62.3%. You received 12.45 out of a possible total of 20 points. Chapter 07 Homework http://session.masteringenvironmentalscience.com/myct/assignmentPrintV… 7 of 7 5/21/2014 8:02 PM

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ENGR216: Mechanics and Vibrations Tutorial sheet 1 Michaelmas Term AY 2015/2016 Problems will be solved in class in week 5 PROBLEM 1 A rod of length L, cross-sectional area A1, and modulus of elasticity E1 has been placed inside a tube of the same length L, but of cross-sectional area A2 and modulus of elasticity E2. A force P is applied on a rigid plate attached to both tube and rod, as shown in the sketch below. Determine: a) the horizontal displacement of the rigid plate; b) the fixed support reactions acting on the rod and tube when E1=E2; c) the fixed support reactions acting on the rod and tube when E1=2E2; HINT: deformation of tube and rod is constrained to be the same. PROBLEM 2 A steel beam has a rectangular cross section of height lx=20 mm and width ly=30 mm, and length lz=1 m (lengths lx, ly and lz are measured respectively along x, y and z axes of a Cartesian system). The material of the beam has Young modulus E=200 GPa, Poisson ratio ν=0.29, and maximum allowable normal stress of 175 MPa. The beam is subject to a compressive centric axial load Pz of 80 KN applied at its ends (load acts along z axis). a) State whether the area of the cross section of the beam will increase or decrease under the effect of the applied centric axial load and explain why. b) Determine the variation of the section height lx in mm, indicating if such variation is a contraction or an elongation. c) Determine the maximum axial load (Pz)max applicable to the beam and the maximum shear stress in these conditions. d) In the loading condition (c), state whether the uniformly distributed normal load to be applied on the beam faces normal to the x axis leading to a zero variation of the section height lx is compressive or tensile and justify your answer. e) In the loading condition (c), determine the magnitude of the uniformly distributed normal load to be applied on the beam faces normal to the x axis resulting in zero variation of the section height lx. f) After application of the uniformly distributed normal load, determine the bulk modulus and the beam dilatation indicating its sign. PROBLEM 3 A beam has a constant circular cross section of radius 20 mm, and is subject to a tensile axial load of 4 KN. a) Determine the magnitude of the maximum stress in the cross section when the axial load is applied at the centre of the section. b) In the loading condition (a), state whether a neutral axis exists or not, and explain why. c) State whether the maximum stress in the cross section when the axial load is applied at 10 mm from the centre of the section is compressive or tensile and explain why. d) In the loading condition (c), determine the magnitude of the maximum compressive and tensile stresses in the cross section. e) In the loading condition (c), determine the distance of the neutral axis from the centre of the cross section. PROBLEM 4 Consider a simply supported beam subject to the distributed load sketched below. a) Determine the equations of shear force V(x) and bending-moment M(x); b) plot V(x) and M(x) along the beam axis; c) assuming the cross section is square and has length a , determine the position along the beam where the maximum normal stress occurs and the value of such maximum normal stress; d) determine the position along the beam where the maximum shear stress occurs and the value of such maximum shear stress.

ENGR216: Mechanics and Vibrations Tutorial sheet 1 Michaelmas Term AY 2015/2016 Problems will be solved in class in week 5 PROBLEM 1 A rod of length L, cross-sectional area A1, and modulus of elasticity E1 has been placed inside a tube of the same length L, but of cross-sectional area A2 and modulus of elasticity E2. A force P is applied on a rigid plate attached to both tube and rod, as shown in the sketch below. Determine: a) the horizontal displacement of the rigid plate; b) the fixed support reactions acting on the rod and tube when E1=E2; c) the fixed support reactions acting on the rod and tube when E1=2E2; HINT: deformation of tube and rod is constrained to be the same. PROBLEM 2 A steel beam has a rectangular cross section of height lx=20 mm and width ly=30 mm, and length lz=1 m (lengths lx, ly and lz are measured respectively along x, y and z axes of a Cartesian system). The material of the beam has Young modulus E=200 GPa, Poisson ratio ν=0.29, and maximum allowable normal stress of 175 MPa. The beam is subject to a compressive centric axial load Pz of 80 KN applied at its ends (load acts along z axis). a) State whether the area of the cross section of the beam will increase or decrease under the effect of the applied centric axial load and explain why. b) Determine the variation of the section height lx in mm, indicating if such variation is a contraction or an elongation. c) Determine the maximum axial load (Pz)max applicable to the beam and the maximum shear stress in these conditions. d) In the loading condition (c), state whether the uniformly distributed normal load to be applied on the beam faces normal to the x axis leading to a zero variation of the section height lx is compressive or tensile and justify your answer. e) In the loading condition (c), determine the magnitude of the uniformly distributed normal load to be applied on the beam faces normal to the x axis resulting in zero variation of the section height lx. f) After application of the uniformly distributed normal load, determine the bulk modulus and the beam dilatation indicating its sign. PROBLEM 3 A beam has a constant circular cross section of radius 20 mm, and is subject to a tensile axial load of 4 KN. a) Determine the magnitude of the maximum stress in the cross section when the axial load is applied at the centre of the section. b) In the loading condition (a), state whether a neutral axis exists or not, and explain why. c) State whether the maximum stress in the cross section when the axial load is applied at 10 mm from the centre of the section is compressive or tensile and explain why. d) In the loading condition (c), determine the magnitude of the maximum compressive and tensile stresses in the cross section. e) In the loading condition (c), determine the distance of the neutral axis from the centre of the cross section. PROBLEM 4 Consider a simply supported beam subject to the distributed load sketched below. a) Determine the equations of shear force V(x) and bending-moment M(x); b) plot V(x) and M(x) along the beam axis; c) assuming the cross section is square and has length a , determine the position along the beam where the maximum normal stress occurs and the value of such maximum normal stress; d) determine the position along the beam where the maximum shear stress occurs and the value of such maximum shear stress.

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