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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Prompt for Essay 2: Argumentative on Drama Write a strongly persuasive essay on one of the following: 1. In Trifles, once the women have pieced together the clues and solved the mystery of Mr. Wright’s death, they quickly come to an agreement to suppress the information from the men who are investigating the murder. Construct an argument in which you identify whether the women were right to withhold their discovery from the investigators or not. 2. In August Wilson’s Fences, are Troy’s problems self-created or is he a victim of his past? Make a convincing argument on this issue. 3. Oedipus downfall in Oedipus the King: fate, freewill or influence of others Take Note as you write all the essays: If you craft your thesis well, it will contain a set of key words, phrases, and ideas which should then show up in key places/transitions throughout your paper. This stylistic and structural practice builds coherence and clarity in your essay. Sub-claims (Reasons) & Evidence (Textual Evidence): Your thesis/main claim statement must be supported by clearly organized evidence drawn primarily from the text of the story itself. Your argument, then, will be arranged with a main claim/thesis, sub-claims (reasons), and textual evidence. Take care to note that your textual evidence (quoted, paraphrased or summarized bits from the story) is not self-evident; it requires explanatory comment preceding it—to direct readers to what specifically in the evidence illustrates your sub-claim and main claim—and often following it for full elaboration and/or recapitulation. • Review the section in A Writer’s Reference on the MLA and Plagiarism • Use Writing Resources in the Course documents tab. MLA Style: Please follow MLA guidelines in formatting, mechanics and stylistics. Papers that do not follow MLA style will not be graded. I advise you look at the sample MLA papers in your textbooks You do not need any secondary source citations or research to support your analysis, but you must cite the source for the story being analyzed and A Writer’s Reference.

Prompt for Essay 2: Argumentative on Drama Write a strongly persuasive essay on one of the following: 1. In Trifles, once the women have pieced together the clues and solved the mystery of Mr. Wright’s death, they quickly come to an agreement to suppress the information from the men who are investigating the murder. Construct an argument in which you identify whether the women were right to withhold their discovery from the investigators or not. 2. In August Wilson’s Fences, are Troy’s problems self-created or is he a victim of his past? Make a convincing argument on this issue. 3. Oedipus downfall in Oedipus the King: fate, freewill or influence of others Take Note as you write all the essays: If you craft your thesis well, it will contain a set of key words, phrases, and ideas which should then show up in key places/transitions throughout your paper. This stylistic and structural practice builds coherence and clarity in your essay. Sub-claims (Reasons) & Evidence (Textual Evidence): Your thesis/main claim statement must be supported by clearly organized evidence drawn primarily from the text of the story itself. Your argument, then, will be arranged with a main claim/thesis, sub-claims (reasons), and textual evidence. Take care to note that your textual evidence (quoted, paraphrased or summarized bits from the story) is not self-evident; it requires explanatory comment preceding it—to direct readers to what specifically in the evidence illustrates your sub-claim and main claim—and often following it for full elaboration and/or recapitulation. • Review the section in A Writer’s Reference on the MLA and Plagiarism • Use Writing Resources in the Course documents tab. MLA Style: Please follow MLA guidelines in formatting, mechanics and stylistics. Papers that do not follow MLA style will not be graded. I advise you look at the sample MLA papers in your textbooks You do not need any secondary source citations or research to support your analysis, but you must cite the source for the story being analyzed and A Writer’s Reference.

1 IN2009: Language Processors Coursework Part 3: The Interpreter Introduction This is the 3rd and final part of the coursework. In the second part of the coursework you created a parser for the Moopl grammar which, given a syntactically correct Moopl program as input, builds an AST representation of the program. In Part 3 you will develop an interpreter which executes Moopl programs by visiting their AST representations. For this part of the coursework we provide functional code (with limitations, see below) for parsing, building a symbol table, type checking and variable allocation. Marks This part of the coursework is worth 12 of the 30 coursework marks for the Language Processors module. This part of the coursework is marked out of 12. Submission deadline This part of the coursework should be handed in before 5pm on Sunday 9th April 2017. In line with school policy, late submissions will be awarded no marks. Return & Feedback Marks and feedback will be available as soon as possible, certainly on or before Wed 3rd May 2017. Plagiarism If you copy the work of others (either that of fellow students or of a third party), with or without their permission, you will score no marks and further disciplinary action will be taken against you. Group working You will be working in the same groups as for the previous parts of the coursework except where group changes have already been approved. Submission: Submit a zip archive (not a rar file) of all your source code (the src folder of your project). We do not want the other parts of your NetBeans project, only the source code. Note 1: Submissions which do not compile will get zero marks. Note 2: You must not change the names or types of any of the existing packages, classes or public methods. 2 Getting started Download either moopl-interp.zip or moopl-interp.tgz from Moodle and extract all files. Key contents to be aware of: • A fully implemented Moopl parser (also implements a parser for the interpreter command language; see below). • A partially implemented Moopl type checker. • Test harnesses for the type checker and interpreter. • A directory of a few example Moopl programs (see Testing below). • Folder interp containing prototype interpreter code. The type-checker is only partially implemented but a more complete implementation will be provided following Session 6. That version is still not fully complete because it doesn’t support inheritance. Part d) below asks you to remove this restriction. The VarAllocator visitor in the interp package uses a simple implementation which only works for methods in which all parameter and local variable names are different. Part e) below asks you to remove this restriction. The three parts below should be attempted in sequence. When you have completed one part you should make a back-up copy of the work and keep it safe, in case you break it in your attempt at the next part. Be sure to test old functionality as well as new (regression testing). We will not assess multiple versions so, if your attempt at part d) or e) breaks previously working code, you may gain a better mark by submitting the earlier version for assessment. c) [8 marks] The Basic Interpreter: complete the implementation of the Interpreter visitor in the interp package. d) [2 marks] Inheritance: extend the type-checker, variable allocator and interpreter to support inheritance. e) [2 marks] Variable Allocation: extend the variable allocator to fully support blockstructure and lexical scoping, removing the requirement that all parameter and local variable names are different. Aim to minimise the number of local variable slots allocated in a stack frame. Note: variable and parameter names declared at the same scope level are still required to be different from each other (a method cannot have two different parameters called x, for example) and this is enforced by the existing typechecking code. But variables declared in different blocks (even when nested) can have the same name. Exceptions Your interpreter will only ever be run on Moopl code which is type-correct (and free from uninitialised local variables). But it is still possible that the Moopl code contains logical errors which may cause runtime errors (such as null-reference or array-bound errors). Your interpreter should throw a MooplRunTimeException with an appropriate error message in these cases. The only kind of exception your interpreter should ever throw is a MooplRunTimeException. 3 Testing The examples folder does not contain a comprehensive test-suite. You need to invent and run your own tests. The document Moopl compared with Java gives a concise summary of how Moopl programs are supposed to behave. You can (and should) also compare the behaviour of your interpreter with that of the online tool: https://smcse.city.ac.uk/student/sj353/langproc/Moopl.html (Note: the online tool checks for uninitialised local variables. Your implementation is not expected to do this.) To test your work, run the top-level Interpret harness, providing the name of a Moopl source file as a command-line argument. When run on a type-correct Moopl source file, Interpret will pretty-print the Moopl program then display a command prompt (>) at which you can enter one of the following commands: :quit This will quit the interpreter. :call main() This will call the top-level proc main, interpreted in the context defined by the Moopl program. (Any top-level proc can be called this way). :eval Exp ; This will evaluate expression Exp, interpreted in the context defined by the Moopl program, and print the result. Note the required terminating semi-colon. Testing your Expression visitors To unit-test your Exp visit methods, run the top-level Interpret harness on a complete Moopl program (though it can be trivial) and use the :eval command. For example, to test your visit methods for the Boolean-literals (ExpTrue and ExpFalse), you would enter the commands > :eval true ; > :eval false ; which should output 1 and 0, respectively. For the most basic cases, the Moopl program is essentially irrelevant (a single top-level proc with empty body may be sufficient). For other cases you will need to write programs containing class definitions (in order, for example, to test object creation and method call). Testing your Statement visitors To unit-test your Stm visit methods, write very simple Moopl programs, each with a top-level proc main() containing just a few lines of code. Run the top-level Interpret harness on these simple programs and enter the command > :call main() You will find a few examples to get you started in the folder examples/unittests. As for the Exp tests, simple cases can be tested using Moopl programs with just a main proc but for the more complex tests you will need to write Moopl programs containing class definitions. 4 Grading criteria Solutions will be graded according to their functional correctness, and the elegance of their implementation. Below are criteria that guide the award of marks. 70 – 100 [1st class] Work that meets all the requirements in full, constructed and presented to a professional standard. Showing evidence of independent reading, thinking and analysis. 60 – 69 [2:1] Work that makes a good attempt to address the requirements, realising all to some extent and most well. Well-structured and well presented. 50 – 59 [2:2] Work that attempts to address requirements realising all to some extent and some well but perhaps also including irrelevant or underdeveloped material. Structure and presentation may not always be clear. 40 – 49 [3rd class] Work that attempts to address the requirements but only realises them to some extent and may not include important elements or be completely accurate. Structure and presentation may lack clarity. 0 – 39 [fail] Unsatisfactory work that does not adequately address the requirements. Structure and presentation may be confused or incoherent.

1 IN2009: Language Processors Coursework Part 3: The Interpreter Introduction This is the 3rd and final part of the coursework. In the second part of the coursework you created a parser for the Moopl grammar which, given a syntactically correct Moopl program as input, builds an AST representation of the program. In Part 3 you will develop an interpreter which executes Moopl programs by visiting their AST representations. For this part of the coursework we provide functional code (with limitations, see below) for parsing, building a symbol table, type checking and variable allocation. Marks This part of the coursework is worth 12 of the 30 coursework marks for the Language Processors module. This part of the coursework is marked out of 12. Submission deadline This part of the coursework should be handed in before 5pm on Sunday 9th April 2017. In line with school policy, late submissions will be awarded no marks. Return & Feedback Marks and feedback will be available as soon as possible, certainly on or before Wed 3rd May 2017. Plagiarism If you copy the work of others (either that of fellow students or of a third party), with or without their permission, you will score no marks and further disciplinary action will be taken against you. Group working You will be working in the same groups as for the previous parts of the coursework except where group changes have already been approved. Submission: Submit a zip archive (not a rar file) of all your source code (the src folder of your project). We do not want the other parts of your NetBeans project, only the source code. Note 1: Submissions which do not compile will get zero marks. Note 2: You must not change the names or types of any of the existing packages, classes or public methods. 2 Getting started Download either moopl-interp.zip or moopl-interp.tgz from Moodle and extract all files. Key contents to be aware of: • A fully implemented Moopl parser (also implements a parser for the interpreter command language; see below). • A partially implemented Moopl type checker. • Test harnesses for the type checker and interpreter. • A directory of a few example Moopl programs (see Testing below). • Folder interp containing prototype interpreter code. The type-checker is only partially implemented but a more complete implementation will be provided following Session 6. That version is still not fully complete because it doesn’t support inheritance. Part d) below asks you to remove this restriction. The VarAllocator visitor in the interp package uses a simple implementation which only works for methods in which all parameter and local variable names are different. Part e) below asks you to remove this restriction. The three parts below should be attempted in sequence. When you have completed one part you should make a back-up copy of the work and keep it safe, in case you break it in your attempt at the next part. Be sure to test old functionality as well as new (regression testing). We will not assess multiple versions so, if your attempt at part d) or e) breaks previously working code, you may gain a better mark by submitting the earlier version for assessment. c) [8 marks] The Basic Interpreter: complete the implementation of the Interpreter visitor in the interp package. d) [2 marks] Inheritance: extend the type-checker, variable allocator and interpreter to support inheritance. e) [2 marks] Variable Allocation: extend the variable allocator to fully support blockstructure and lexical scoping, removing the requirement that all parameter and local variable names are different. Aim to minimise the number of local variable slots allocated in a stack frame. Note: variable and parameter names declared at the same scope level are still required to be different from each other (a method cannot have two different parameters called x, for example) and this is enforced by the existing typechecking code. But variables declared in different blocks (even when nested) can have the same name. Exceptions Your interpreter will only ever be run on Moopl code which is type-correct (and free from uninitialised local variables). But it is still possible that the Moopl code contains logical errors which may cause runtime errors (such as null-reference or array-bound errors). Your interpreter should throw a MooplRunTimeException with an appropriate error message in these cases. The only kind of exception your interpreter should ever throw is a MooplRunTimeException. 3 Testing The examples folder does not contain a comprehensive test-suite. You need to invent and run your own tests. The document Moopl compared with Java gives a concise summary of how Moopl programs are supposed to behave. You can (and should) also compare the behaviour of your interpreter with that of the online tool: https://smcse.city.ac.uk/student/sj353/langproc/Moopl.html (Note: the online tool checks for uninitialised local variables. Your implementation is not expected to do this.) To test your work, run the top-level Interpret harness, providing the name of a Moopl source file as a command-line argument. When run on a type-correct Moopl source file, Interpret will pretty-print the Moopl program then display a command prompt (>) at which you can enter one of the following commands: :quit This will quit the interpreter. :call main() This will call the top-level proc main, interpreted in the context defined by the Moopl program. (Any top-level proc can be called this way). :eval Exp ; This will evaluate expression Exp, interpreted in the context defined by the Moopl program, and print the result. Note the required terminating semi-colon. Testing your Expression visitors To unit-test your Exp visit methods, run the top-level Interpret harness on a complete Moopl program (though it can be trivial) and use the :eval command. For example, to test your visit methods for the Boolean-literals (ExpTrue and ExpFalse), you would enter the commands > :eval true ; > :eval false ; which should output 1 and 0, respectively. For the most basic cases, the Moopl program is essentially irrelevant (a single top-level proc with empty body may be sufficient). For other cases you will need to write programs containing class definitions (in order, for example, to test object creation and method call). Testing your Statement visitors To unit-test your Stm visit methods, write very simple Moopl programs, each with a top-level proc main() containing just a few lines of code. Run the top-level Interpret harness on these simple programs and enter the command > :call main() You will find a few examples to get you started in the folder examples/unittests. As for the Exp tests, simple cases can be tested using Moopl programs with just a main proc but for the more complex tests you will need to write Moopl programs containing class definitions. 4 Grading criteria Solutions will be graded according to their functional correctness, and the elegance of their implementation. Below are criteria that guide the award of marks. 70 – 100 [1st class] Work that meets all the requirements in full, constructed and presented to a professional standard. Showing evidence of independent reading, thinking and analysis. 60 – 69 [2:1] Work that makes a good attempt to address the requirements, realising all to some extent and most well. Well-structured and well presented. 50 – 59 [2:2] Work that attempts to address requirements realising all to some extent and some well but perhaps also including irrelevant or underdeveloped material. Structure and presentation may not always be clear. 40 – 49 [3rd class] Work that attempts to address the requirements but only realises them to some extent and may not include important elements or be completely accurate. Structure and presentation may lack clarity. 0 – 39 [fail] Unsatisfactory work that does not adequately address the requirements. Structure and presentation may be confused or incoherent.

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Sex, Gender, and Popular Culture Spring 2015 Look through popular magazines, and see if you can find advertisements that objectify women in order to sell a product. Alternately, you may use an advertisement on television (but make sure to provide a link to the ad so I can see it!). Study these images then write a paper about objectification that deals with all or some of the following: • What effect(s), if any, do you think the objectification of women’s bodies has on our culture? • Jean Kilbourne states “turning a human being into a thing is almost always the first step toward justifying violence against that person.” What do you think she means by this? Do you agree with her reasoning? Why or why not? • Some people would argue that depicting a woman’s body as an object is a form of art. What is your opinion of this point of view? Explain your reasoning. • Why do you think that women are objectified more often than men are? • How does sexualization and objectification play out differently across racial lines? • Kilbourne explains that the consequences of being objectified are different – and more serious – for women than for men. Do you agree? How is the world different for women than it is for men? How do objectified images of women interact with those in our culture differently from the way images of men do? Why is it important to look at images in the context of the culture? • What is the difference between sexual objectification and sexual subjectification? (Ros Gill ) • How do ads construct violent white masculinity and how does that vision of masculinity hurt both men and women? Throughout your written analysis, be sure to make clear and specific reference to the images you selected, and please submit these images with your paper. Make sure you engage with and reference to at least 4 of the following authors: Kilbourne, Bordo, Hunter & Soto, Rose, Durham, Gill, Katz, Schuchardt, Ono and Buescher. Guidelines:  Keep your content focused on structural, systemic, institutional factors rather than the individual: BE ANALYTICAL NOT ANECDOTAL.  Avoid using the first person or including personal stories/reactions. You must make sure to actively engage with your readings: these essays need to be informed and framed by the theoretical material you have been reading this semester.  Keep within the 4-6 page limit; use 12-point font, double spacing and 1-inch margins.  Use formal writing conventions (introduction/thesis statement, body, conclusion) and correct grammar. Resources may be cited within the text of your paper, i.e. (Walters, 2013).

Sex, Gender, and Popular Culture Spring 2015 Look through popular magazines, and see if you can find advertisements that objectify women in order to sell a product. Alternately, you may use an advertisement on television (but make sure to provide a link to the ad so I can see it!). Study these images then write a paper about objectification that deals with all or some of the following: • What effect(s), if any, do you think the objectification of women’s bodies has on our culture? • Jean Kilbourne states “turning a human being into a thing is almost always the first step toward justifying violence against that person.” What do you think she means by this? Do you agree with her reasoning? Why or why not? • Some people would argue that depicting a woman’s body as an object is a form of art. What is your opinion of this point of view? Explain your reasoning. • Why do you think that women are objectified more often than men are? • How does sexualization and objectification play out differently across racial lines? • Kilbourne explains that the consequences of being objectified are different – and more serious – for women than for men. Do you agree? How is the world different for women than it is for men? How do objectified images of women interact with those in our culture differently from the way images of men do? Why is it important to look at images in the context of the culture? • What is the difference between sexual objectification and sexual subjectification? (Ros Gill ) • How do ads construct violent white masculinity and how does that vision of masculinity hurt both men and women? Throughout your written analysis, be sure to make clear and specific reference to the images you selected, and please submit these images with your paper. Make sure you engage with and reference to at least 4 of the following authors: Kilbourne, Bordo, Hunter & Soto, Rose, Durham, Gill, Katz, Schuchardt, Ono and Buescher. Guidelines:  Keep your content focused on structural, systemic, institutional factors rather than the individual: BE ANALYTICAL NOT ANECDOTAL.  Avoid using the first person or including personal stories/reactions. You must make sure to actively engage with your readings: these essays need to be informed and framed by the theoretical material you have been reading this semester.  Keep within the 4-6 page limit; use 12-point font, double spacing and 1-inch margins.  Use formal writing conventions (introduction/thesis statement, body, conclusion) and correct grammar. Resources may be cited within the text of your paper, i.e. (Walters, 2013).

The objectification of women has been a very controversial topic … Read More...
Which statement about DNA replication is FALSE? The lagging strand is made of a series of pieces that must be joined together to make a continuous strand. The two strands of parental DNA are separated during DNA replication. DNA polymerase builds a new strand by adding DNA nucleotides one at a time. Because the two strands of parental DNA run in opposite directions, the new strands must be made in different ways. DNA ligase adds nucleotides to the lagging strand.

Which statement about DNA replication is FALSE? The lagging strand is made of a series of pieces that must be joined together to make a continuous strand. The two strands of parental DNA are separated during DNA replication. DNA polymerase builds a new strand by adding DNA nucleotides one at a time. Because the two strands of parental DNA run in opposite directions, the new strands must be made in different ways. DNA ligase adds nucleotides to the lagging strand.

DNA ligase adds nucleotides to the lagging strand.   Which … Read More...