10.2 California Imaging Center, a not-for-profit business, is evaluating the purchase of new diagnostic equipment. The equipment, which costs $600,000 has an expected life of five years and an estimated salvage value of $200,000 at that time. The equipment is expected to be used 15 times a day for 250 days a year for each year of the project’s life. On average, each procedure is expected to generate $80 in cash collections during the first year of use. Thus, net revenues for Year 1 are estimated at 15 X 250 X $80 =$300,000. Labor and maintenance costs are expected to be $100,000 during the first year of operation, while utilities will cost another $10,000 and cash overhead will increase by $5,000 in Year 1. The cost for expendable supplies is expected to average $5 per procedure during the first year. All costs and revenues are expected to increase at 5 percent inflation rate after the first year. The center’s corporate cost of capital is 10 percent. a. Estimate the project’s net cash flows over its five-year estimated life. (hint: use the following format as a guide.) Year 0 1 2 3 4 5 Equipment Cost Net revenues Less: labor/maintenance costs Utilities cost Supplies Incremental overhead Operating income Equipment salvage value Net cash flow b. What are the project’s NPV and IRR? (Assume for now that the project has average risk.) c. Assume the project is assessed to have high risk and California Imaging Center adds or subtracts 3 percentage points to adjust for project risk. Now, what is the project’s NPV? Does the risk assessment change how the project’s IRR is interpreted?

10.2 California Imaging Center, a not-for-profit business, is evaluating the purchase of new diagnostic equipment. The equipment, which costs $600,000 has an expected life of five years and an estimated salvage value of $200,000 at that time. The equipment is expected to be used 15 times a day for 250 days a year for each year of the project’s life. On average, each procedure is expected to generate $80 in cash collections during the first year of use. Thus, net revenues for Year 1 are estimated at 15 X 250 X $80 =$300,000. Labor and maintenance costs are expected to be $100,000 during the first year of operation, while utilities will cost another $10,000 and cash overhead will increase by $5,000 in Year 1. The cost for expendable supplies is expected to average $5 per procedure during the first year. All costs and revenues are expected to increase at 5 percent inflation rate after the first year. The center’s corporate cost of capital is 10 percent. a. Estimate the project’s net cash flows over its five-year estimated life. (hint: use the following format as a guide.) Year 0 1 2 3 4 5 Equipment Cost Net revenues Less: labor/maintenance costs Utilities cost Supplies Incremental overhead Operating income Equipment salvage value Net cash flow b. What are the project’s NPV and IRR? (Assume for now that the project has average risk.) c. Assume the project is assessed to have high risk and California Imaging Center adds or subtracts 3 percentage points to adjust for project risk. Now, what is the project’s NPV? Does the risk assessment change how the project’s IRR is interpreted?

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Math 285 Quiz One Name: ________________ 1. The product of these two matrices 5 2 2 −1  4 −2 1 3  is (Please show your work for full credit.) 2. For what value of a is this determinant equal to 0? 0 5 2 0 1 −8 −4 2 (please justify your answer.) 3. What is the product of these matrices? 3 2 6 −2 1 0 4 1 0   2346  (Please justify your answer.) 4. What is the largest possible number of pivots a 7 × 5 matrix can have? (Please justify your answer.) Homework 1 5. Find the standard matrix of the linear transformation : →  which rotates a point about the origin through an angle of   radians (counterclockwise). True or False (Simply enter T or F, no need to justify the answer) If matrices  and  are row equivalent, they have the same reduced echelon form. In general,  +  ≠  +  (assume  and  are  x  matrices). If a matrix  is symmetric, then so is  + “#. A matrix  must be a square matrix to be invertible. If $%&’( ≠ 0, then columns of  are linearly independent. If an  x  matrix  is equivalent to “#, then )* is also equivalent to “#. If an + x  matrix  has a pivot position in every row, then the equation , = . has a unique solution for each . in /0. If  = “, then  is invertible.

Math 285 Quiz One Name: ________________ 1. The product of these two matrices 5 2 2 −1  4 −2 1 3  is (Please show your work for full credit.) 2. For what value of a is this determinant equal to 0? 0 5 2 0 1 −8 −4 2 (please justify your answer.) 3. What is the product of these matrices? 3 2 6 −2 1 0 4 1 0   2346  (Please justify your answer.) 4. What is the largest possible number of pivots a 7 × 5 matrix can have? (Please justify your answer.) Homework 1 5. Find the standard matrix of the linear transformation : →  which rotates a point about the origin through an angle of   radians (counterclockwise). True or False (Simply enter T or F, no need to justify the answer) If matrices  and  are row equivalent, they have the same reduced echelon form. In general,  +  ≠  +  (assume  and  are  x  matrices). If a matrix  is symmetric, then so is  + “#. A matrix  must be a square matrix to be invertible. If $%&’( ≠ 0, then columns of  are linearly independent. If an  x  matrix  is equivalent to “#, then )* is also equivalent to “#. If an + x  matrix  has a pivot position in every row, then the equation , = . has a unique solution for each . in /0. If  = “, then  is invertible.

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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 8 Due: 11:59pm on Friday, April 4, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Conceptual Question 10.3 Part A If a particle’s speed increases by a factor of 5, by what factor does its kinetic energy change? ANSWER: Correct Conceptual Question 10.11 A spring is compressed 1.5 . Part A How far must you compress a spring with twice the spring constant to store the same amount of energy? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct = 25 K2 K1 cm x = 1.1 cm Problem 10.2 The lowest point in Death Valley is below sea level. The summit of nearby Mt. Whitney has an elevation of 4420 . Part A What is the change in potential energy of an energetic 80 hiker who makes it from the floor of Death Valley to the top of Mt.Whitney? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 10.3 Part A At what speed does a 1800 compact car have the same kinetic energy as a 1.80×104 truck going 21.0 ? Express your answer with the appropriate units. ANSWER: Correct Problem 10.5 A boy reaches out of a window and tosses a ball straight up with a speed of 13 . The ball is 21 above the ground as he releases it. 85m m kg U = 3.5×106 J kg kg km/hr vc = 66.4 km hr m/s m Part A Use energy to find the ball’s maximum height above the ground. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B Use energy to find the ball’s speed as it passes the window on its way down. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C Use energy to find the speed of impact on the ground. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Hmax = 30 m v = 13 ms v = 24 ms Problem 10.8 A 59.0 skateboarder wants to just make it to the upper edge of a “quarter pipe,” a track that is one-quarter of a circle with a radius of 2.30 . Part A What speed does he need at the bottom? Express your answer with the appropriate units. ANSWER: Correct Problem 10.12 A 1500 car traveling at 12 suddenly runs out of gas while approaching the valley shown in the figure. The alert driver immediately puts the car in neutral so that it will roll. Part A kg m 6.71 ms kg m/s What will be the car’s speed as it coasts into the gas station on the other side of the valley? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Ups and Downs Learning Goal: To apply the law of conservation of energy to an object launched upward in the gravitational field of the earth. In the absence of nonconservative forces such as friction and air resistance, the total mechanical energy in a closed system is conserved. This is one particular case of the law of conservation of energy. In this problem, you will apply the law of conservation of energy to different objects launched from the earth. The energy transformations that take place involve the object’s kinetic energy and its gravitational potential energy . The law of conservation of energy for such cases implies that the sum of the object’s kinetic energy and potential energy does not change with time. This idea can be expressed by the equation , where “i” denotes the “initial” moment and “f” denotes the “final” moment. Since any two moments will work, the choice of the moments to consider is, technically, up to you. That choice, though, is usually suggested by the question posed in the problem. First, let us consider an object launched vertically upward with an initial speed . Neglect air resistance. Part A As the projectile goes upward, what energy changes take place? ANSWER: v = 6.8 ms K = (1/2)mv2 U = mgh Ki + Ui = Kf + Uf v Correct Part B At the top point of the flight, what can be said about the projectile’s kinetic and potential energy? ANSWER: Correct Strictly speaking, it is not the ball that possesses potential energy; rather, it is the system “Earth-ball.” Although we will often talk about “the gravitational potential energy of an elevated object,” it is useful to keep in mind that the energy, in fact, is associated with the interactions between the earth and the elevated object. Part C The potential energy of the object at the moment of launch __________. ANSWER: Both kinetic and potential energy decrease. Both kinetic and potential energy increase. Kinetic energy decreases; potential energy increases. Kinetic energy increases; potential energy decreases. Both kinetic and potential energy are at their maximum values. Both kinetic and potential energy are at their minimum values. Kinetic energy is at a maximum; potential energy is at a minimum. Kinetic energy is at a minimum; potential energy is at a maximum. Correct Usually, the zero level is chosen so as to make the relevant calculations simpler. In this case, it makes good sense to assume that at the ground level–but this is not, by any means, the only choice! Part D Using conservation of energy, find the maximum height to which the object will rise. Express your answer in terms of and the magnitude of the acceleration of gravity . ANSWER: Correct You may remember this result from kinematics. It is comforting to know that our new approach yields the same answer. Part E At what height above the ground does the projectile have a speed of ? Express your answer in terms of and the magnitude of the acceleration of gravity . ANSWER: is negative is positive is zero depends on the choice of the “zero level” of potential energy U = 0 hmax v g hmax = v2 2g h 0.5v v g h = 3 v2 8g Correct Part F What is the speed of the object at the height of ? Express your answer in terms of and . Use three significant figures in the numeric coefficient. Hint 1. How to approach the problem You are being asked for the speed at half of the maximum height. You know that at the initial height ( ), the speed is . All of the energy is kinetic energy, and so, the total energy is . At the maximum height, all of the energy is potential energy. Since the gravitational potential energy is proportional to , half of the initial kinetic energy must have been converted to potential energy when the projectile is at . Thus, the kinetic energy must be half of its original value (i.e., when ). You need to determine the speed, as a multiple of , that corresponds to such a kinetic energy. ANSWER: Correct Let us now consider objects launched at an angle. For such situations, using conservation of energy leads to a quicker solution than can be produced by kinematics. Part G A ball is launched as a projectile with initial speed at an angle above the horizontal. Using conservation of energy, find the maximum height of the ball’s flight. Express your answer in terms of , , and . Hint 1. Find the final kinetic energy Find the final kinetic energy of the ball. Here, the best choice of “final” moment is the point at which the ball reaches its maximum height, since this is the point we are interested in. u (1/2)hmax v g h = 0 v (1/2)mv2 h (1/2)hmax (1/4)mv2 h = (1/2)hmax v u = 0.707v v hmax v g Kf Express your answer in terms of , , and . Hint 1. Find the speed at the maximum height The speed of the ball at the maximum height is __________. ANSWER: ANSWER: ANSWER: Correct Part H A ball is launched with initial speed from ground level up a frictionless slope. The slope makes an angle with the horizontal. Using conservation of energy, find the maximum vertical height to which the ball will climb. Express your answer in terms of , , and . You may or may not use all of these quantities. v m 0 v v cos v sin v tan Kf = 0.5m(vcos( ))2 hmax = (vsin( ))2 2g v hmax v g ANSWER: Correct Interestingly, the answer does not depend on . The difference between this situation and the projectile case is that the ball moving up a slope has no kinetic energy at the top of its trajectory whereas the projectile launched at an angle does. Part I A ball is launched with initial speed from the ground level up a frictionless hill. The hill becomes steeper as the ball slides up; however, the ball remains in contact with the hill at all times. Using conservation of energy, find the maximum vertical height to which the ball will climb. Express your answer in terms of and . ANSWER: Correct The profile of the hill does not matter; the equation would have the same terms regardless of the steepness of the hill. Problem 10.14 A 12- -long spring is attached to the ceiling. When a 2.2 mass is hung from it, the spring stretches to a length of 17 . Part A What is the spring constant ? Express your answer to two significant figures and include the appropriate units. hmax = v2 2g v hmax v g hmax = v2 2g Ki + Ui = Kf + Uf cm kg cm k ANSWER: Correct Part B How long is the spring when a 3.0 mass is suspended from it? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Enhanced EOC: Problem 10.17 A 6.2 mass hanging from a spring scale is slowly lowered onto a vertical spring, as shown in . You may want to review ( pages 255 – 257) . For help with math skills, you may want to review: Solving Algebraic Equations = 430 k Nm kg y = 19 cm kg Part A What does the spring scale read just before the mass touches the lower spring? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture showing the forces acting on the mass before it touches the scale. What is the net force on the mass? What is the force on the mass due to gravity? What is the force on the mass due to the scale? ANSWER: Correct Part B The scale reads 22 when the lower spring has been compressed by 2.7 . What is the value of the spring constant for the lower spring? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture showing the forces acting on the mass. What is the net force on the mass? What is the force on the mass due to gravity? What is the force on the mass due to the scale? Use these to determine the force on the mass by the spring, taking note of the directions from your picture. How is the spring constant related to the force by the spring and the compression of the spring? Check your units. ANSWER: F = 61 N N cm k = 1400 k Nm Correct Part C At what compression length will the scale read zero? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture showing the forces on the mass. When the scale reads zero, what is the force on the mass due to the scale? What is the gravitational force on the mass? What is the force on the mass by the spring? How is the compression length related to the force by the spring and the spring constant? Check your units. ANSWER: Correct Problem 10.18 Part A How far must you stretch a spring with = 800 to store 180 of energy? Express your answer to two significant figures and include the appropriate units. ANSWER: y = 4.2 cm k N/m J Correct Problem 10.22 A 15 runaway grocery cart runs into a spring with spring constant 230 and compresses it by 57 . Part A What was the speed of the cart just before it hit the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Spring Gun A spring-loaded toy gun is used to shoot a ball straight up in the air. The ball reaches a maximum height , measured from the equilibrium position of the spring. s = 0.67 m kg N/m cm v = 2.2 ms H Part A The same ball is shot straight up a second time from the same gun, but this time the spring is compressed only half as far before firing. How far up does the ball go this time? Neglect friction. Assume that the spring is ideal and that the distance by which the spring is compressed is negligible compared to . Hint 1. Potential energy of the spring The potential energy of a spring is proportional to the square of the distance the spring is compressed. The spring was compressed half the distance, so the mass, when launched, has one quarter of the energy as in the first trial. Hint 2. Potential energy of the ball At the highest point in the ball’s trajectory, all of the spring’s potential energy has been converted into gravitational potential energy of the ball. ANSWER: Correct A Bullet Is Fired into a Wooden Block A bullet of mass is fired horizontally with speed at a wooden block of mass resting on a frictionless table. The bullet hits the block and becomes completely embedded within it. After the bullet has come to rest within the block, the block, with the bullet in it, is traveling at speed . H height = H 4 mb vi mw vf Part A Which of the following best describes this collision? Hint 1. Types of collisions An inelastic collision is a collision in which kinetic energy is not conserved. In a partially inelastic collision, kinetic energy is lost, but the objects colliding do not stick together. From this information, you can infer what completely inelastic and elastic collisions are. ANSWER: Correct Part B Which of the following quantities, if any, are conserved during this collision? Hint 1. When is kinetic energy conserved? Kinetic energy is conserved only in perfectly elastic collisions. ANSWER: perfectly elastic partially inelastic perfectly inelastic Correct Part C What is the speed of the block/bullet system after the collision? Express your answer in terms of , , and . Hint 1. Find the momentum after the collision What is the total momentum of the block/bullet system after the collision? Express your answer in terms of and other given quantities. ANSWER: Hint 2. Use conservation of momentum The momentum of the block/bullet system is conserved. Therefore, the momentum before the collision is the same as the momentum after the collision. Find a second expression for , this time expressed as the total momentum of the system before the collision. Express your answer in terms of and other given quantities. ANSWER: kinetic energy only momentum only kinetic energy and momentum neither momentum nor kinetic energy vi mw mb ptotal vf ptotal = (mw + mb)vf ptotal vi ptotal = mbvi ANSWER: Correct Problem 10.31 Ball 1, with a mass of 150 and traveling at 15.0 , collides head on with ball 2, which has a mass of 340 and is initially at rest. Part A What are the final velocities of each ball if the collision is perfectly elastic? Express your answer with the appropriate units. ANSWER: Correct Part B Express your answer with the appropriate units. ANSWER: Correct Part C vf = mb vi mb+mw g m/s g (vfx) = -5.82 1 ms (vfx) = 9.18 2 ms What are the final velocities of each ball if the collision is perfectly inelastic? Express your answer with the appropriate units. ANSWER: Correct Part D Express your answer with the appropriate units. ANSWER: Correct Enhanced EOC: Problem 10.43 A package of mass is released from rest at a warehouse loading dock and slides down the = 2.2 – high, frictionless chute to a waiting truck. Unfortunately, the truck driver went on a break without having removed the previous package, of mass , from the bottom of the chute. You may want to review ( pages 265 – 269) . For help with math skills, you may want to review: Solving Algebraic Equations (vfx) = 4.59 1 ms (vfx) = 4.59 2 ms m h m 2m Part A Suppose the packages stick together. What is their common speed after the collision? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem There are two parts to this problem: the block sliding down the frictionless incline and the collision. What conservation laws are valid in each part? In terms of , what are the kinetic and potential energies of the block at the top of the incline? What is the potential energy of the same block at the bottom just before the collision? What are the kinetic energy and velocity of block just before the collision? What is conserved during the collision? What is the total momentum of the two blocks before the collision? What is the momentum of the two blocks stuck together after the collision? What is the velocity of the two blocks after the collision? ANSWER: Correct Part B Suppose the collision between the packages is perfectly elastic. To what height does the package of mass rebound? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem There are three parts to this problem: the block sliding down the incline, the collision, and mass going back up the incline. What conservation laws are valid in each part? m m v = 2.2 ms m m What is an elastic collision? For an elastic collision, how are the initial and final velocities related when one of the masses is initially at rest? Using the velocity of just before the collision from Part A, what is the velocity of just after the collision in this case? What are the kinetic and potential energies of mass just after the collision? What is the kinetic energy of mass at its maximum rebound height? Using conservation of energy, what is the potential energy of mass at its maximum height? What is the maximum height? ANSWER: Correct Problem 10.35 A cannon tilted up at a 35.0 angle fires a cannon ball at 79.0 from atop a 21.0 -high fortress wall. Part A What is the ball’s impact speed on the ground below? Express your answer with the appropriate units. ANSWER: Correct Problem 10.45 A 1000 safe is 2.5 above a heavy-duty spring when the rope holding the safe breaks. The safe hits the spring and compresses it 48 . m m m m m h = 24 cm $ m/s m vf = 81.6 ms kg m cm Part A What is the spring constant of the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 10.49 A 100 block on a frictionless table is firmly attached to one end of a spring with = 21 . The other end of the spring is anchored to the wall. A 30 ball is thrown horizontally toward the block with a speed of 6.0 . Part A If the collision is perfectly elastic, what is the ball’s speed immediately after the collision? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the maximum compression of the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: = 2.5×105 k Nm g k N/m g m/s v = 3.2 ms Correct Part C Repeat part A for the case of a perfectly inelastic collision. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part D Repeat part B for the case of a perfectly inelastic collision. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Score Summary: Your score on this assignment is 99.4%. You received 120.28 out of a possible total of 121 points. x = 0.19 m v = 1.4 ms x = 0.11 m

Assignment 8 Due: 11:59pm on Friday, April 4, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Conceptual Question 10.3 Part A If a particle’s speed increases by a factor of 5, by what factor does its kinetic energy change? ANSWER: Correct Conceptual Question 10.11 A spring is compressed 1.5 . Part A How far must you compress a spring with twice the spring constant to store the same amount of energy? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct = 25 K2 K1 cm x = 1.1 cm Problem 10.2 The lowest point in Death Valley is below sea level. The summit of nearby Mt. Whitney has an elevation of 4420 . Part A What is the change in potential energy of an energetic 80 hiker who makes it from the floor of Death Valley to the top of Mt.Whitney? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 10.3 Part A At what speed does a 1800 compact car have the same kinetic energy as a 1.80×104 truck going 21.0 ? Express your answer with the appropriate units. ANSWER: Correct Problem 10.5 A boy reaches out of a window and tosses a ball straight up with a speed of 13 . The ball is 21 above the ground as he releases it. 85m m kg U = 3.5×106 J kg kg km/hr vc = 66.4 km hr m/s m Part A Use energy to find the ball’s maximum height above the ground. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B Use energy to find the ball’s speed as it passes the window on its way down. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C Use energy to find the speed of impact on the ground. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Hmax = 30 m v = 13 ms v = 24 ms Problem 10.8 A 59.0 skateboarder wants to just make it to the upper edge of a “quarter pipe,” a track that is one-quarter of a circle with a radius of 2.30 . Part A What speed does he need at the bottom? Express your answer with the appropriate units. ANSWER: Correct Problem 10.12 A 1500 car traveling at 12 suddenly runs out of gas while approaching the valley shown in the figure. The alert driver immediately puts the car in neutral so that it will roll. Part A kg m 6.71 ms kg m/s What will be the car’s speed as it coasts into the gas station on the other side of the valley? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Ups and Downs Learning Goal: To apply the law of conservation of energy to an object launched upward in the gravitational field of the earth. In the absence of nonconservative forces such as friction and air resistance, the total mechanical energy in a closed system is conserved. This is one particular case of the law of conservation of energy. In this problem, you will apply the law of conservation of energy to different objects launched from the earth. The energy transformations that take place involve the object’s kinetic energy and its gravitational potential energy . The law of conservation of energy for such cases implies that the sum of the object’s kinetic energy and potential energy does not change with time. This idea can be expressed by the equation , where “i” denotes the “initial” moment and “f” denotes the “final” moment. Since any two moments will work, the choice of the moments to consider is, technically, up to you. That choice, though, is usually suggested by the question posed in the problem. First, let us consider an object launched vertically upward with an initial speed . Neglect air resistance. Part A As the projectile goes upward, what energy changes take place? ANSWER: v = 6.8 ms K = (1/2)mv2 U = mgh Ki + Ui = Kf + Uf v Correct Part B At the top point of the flight, what can be said about the projectile’s kinetic and potential energy? ANSWER: Correct Strictly speaking, it is not the ball that possesses potential energy; rather, it is the system “Earth-ball.” Although we will often talk about “the gravitational potential energy of an elevated object,” it is useful to keep in mind that the energy, in fact, is associated with the interactions between the earth and the elevated object. Part C The potential energy of the object at the moment of launch __________. ANSWER: Both kinetic and potential energy decrease. Both kinetic and potential energy increase. Kinetic energy decreases; potential energy increases. Kinetic energy increases; potential energy decreases. Both kinetic and potential energy are at their maximum values. Both kinetic and potential energy are at their minimum values. Kinetic energy is at a maximum; potential energy is at a minimum. Kinetic energy is at a minimum; potential energy is at a maximum. Correct Usually, the zero level is chosen so as to make the relevant calculations simpler. In this case, it makes good sense to assume that at the ground level–but this is not, by any means, the only choice! Part D Using conservation of energy, find the maximum height to which the object will rise. Express your answer in terms of and the magnitude of the acceleration of gravity . ANSWER: Correct You may remember this result from kinematics. It is comforting to know that our new approach yields the same answer. Part E At what height above the ground does the projectile have a speed of ? Express your answer in terms of and the magnitude of the acceleration of gravity . ANSWER: is negative is positive is zero depends on the choice of the “zero level” of potential energy U = 0 hmax v g hmax = v2 2g h 0.5v v g h = 3 v2 8g Correct Part F What is the speed of the object at the height of ? Express your answer in terms of and . Use three significant figures in the numeric coefficient. Hint 1. How to approach the problem You are being asked for the speed at half of the maximum height. You know that at the initial height ( ), the speed is . All of the energy is kinetic energy, and so, the total energy is . At the maximum height, all of the energy is potential energy. Since the gravitational potential energy is proportional to , half of the initial kinetic energy must have been converted to potential energy when the projectile is at . Thus, the kinetic energy must be half of its original value (i.e., when ). You need to determine the speed, as a multiple of , that corresponds to such a kinetic energy. ANSWER: Correct Let us now consider objects launched at an angle. For such situations, using conservation of energy leads to a quicker solution than can be produced by kinematics. Part G A ball is launched as a projectile with initial speed at an angle above the horizontal. Using conservation of energy, find the maximum height of the ball’s flight. Express your answer in terms of , , and . Hint 1. Find the final kinetic energy Find the final kinetic energy of the ball. Here, the best choice of “final” moment is the point at which the ball reaches its maximum height, since this is the point we are interested in. u (1/2)hmax v g h = 0 v (1/2)mv2 h (1/2)hmax (1/4)mv2 h = (1/2)hmax v u = 0.707v v hmax v g Kf Express your answer in terms of , , and . Hint 1. Find the speed at the maximum height The speed of the ball at the maximum height is __________. ANSWER: ANSWER: ANSWER: Correct Part H A ball is launched with initial speed from ground level up a frictionless slope. The slope makes an angle with the horizontal. Using conservation of energy, find the maximum vertical height to which the ball will climb. Express your answer in terms of , , and . You may or may not use all of these quantities. v m 0 v v cos v sin v tan Kf = 0.5m(vcos( ))2 hmax = (vsin( ))2 2g v hmax v g ANSWER: Correct Interestingly, the answer does not depend on . The difference between this situation and the projectile case is that the ball moving up a slope has no kinetic energy at the top of its trajectory whereas the projectile launched at an angle does. Part I A ball is launched with initial speed from the ground level up a frictionless hill. The hill becomes steeper as the ball slides up; however, the ball remains in contact with the hill at all times. Using conservation of energy, find the maximum vertical height to which the ball will climb. Express your answer in terms of and . ANSWER: Correct The profile of the hill does not matter; the equation would have the same terms regardless of the steepness of the hill. Problem 10.14 A 12- -long spring is attached to the ceiling. When a 2.2 mass is hung from it, the spring stretches to a length of 17 . Part A What is the spring constant ? Express your answer to two significant figures and include the appropriate units. hmax = v2 2g v hmax v g hmax = v2 2g Ki + Ui = Kf + Uf cm kg cm k ANSWER: Correct Part B How long is the spring when a 3.0 mass is suspended from it? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Enhanced EOC: Problem 10.17 A 6.2 mass hanging from a spring scale is slowly lowered onto a vertical spring, as shown in . You may want to review ( pages 255 – 257) . For help with math skills, you may want to review: Solving Algebraic Equations = 430 k Nm kg y = 19 cm kg Part A What does the spring scale read just before the mass touches the lower spring? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture showing the forces acting on the mass before it touches the scale. What is the net force on the mass? What is the force on the mass due to gravity? What is the force on the mass due to the scale? ANSWER: Correct Part B The scale reads 22 when the lower spring has been compressed by 2.7 . What is the value of the spring constant for the lower spring? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture showing the forces acting on the mass. What is the net force on the mass? What is the force on the mass due to gravity? What is the force on the mass due to the scale? Use these to determine the force on the mass by the spring, taking note of the directions from your picture. How is the spring constant related to the force by the spring and the compression of the spring? Check your units. ANSWER: F = 61 N N cm k = 1400 k Nm Correct Part C At what compression length will the scale read zero? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem Draw a picture showing the forces on the mass. When the scale reads zero, what is the force on the mass due to the scale? What is the gravitational force on the mass? What is the force on the mass by the spring? How is the compression length related to the force by the spring and the spring constant? Check your units. ANSWER: Correct Problem 10.18 Part A How far must you stretch a spring with = 800 to store 180 of energy? Express your answer to two significant figures and include the appropriate units. ANSWER: y = 4.2 cm k N/m J Correct Problem 10.22 A 15 runaway grocery cart runs into a spring with spring constant 230 and compresses it by 57 . Part A What was the speed of the cart just before it hit the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Spring Gun A spring-loaded toy gun is used to shoot a ball straight up in the air. The ball reaches a maximum height , measured from the equilibrium position of the spring. s = 0.67 m kg N/m cm v = 2.2 ms H Part A The same ball is shot straight up a second time from the same gun, but this time the spring is compressed only half as far before firing. How far up does the ball go this time? Neglect friction. Assume that the spring is ideal and that the distance by which the spring is compressed is negligible compared to . Hint 1. Potential energy of the spring The potential energy of a spring is proportional to the square of the distance the spring is compressed. The spring was compressed half the distance, so the mass, when launched, has one quarter of the energy as in the first trial. Hint 2. Potential energy of the ball At the highest point in the ball’s trajectory, all of the spring’s potential energy has been converted into gravitational potential energy of the ball. ANSWER: Correct A Bullet Is Fired into a Wooden Block A bullet of mass is fired horizontally with speed at a wooden block of mass resting on a frictionless table. The bullet hits the block and becomes completely embedded within it. After the bullet has come to rest within the block, the block, with the bullet in it, is traveling at speed . H height = H 4 mb vi mw vf Part A Which of the following best describes this collision? Hint 1. Types of collisions An inelastic collision is a collision in which kinetic energy is not conserved. In a partially inelastic collision, kinetic energy is lost, but the objects colliding do not stick together. From this information, you can infer what completely inelastic and elastic collisions are. ANSWER: Correct Part B Which of the following quantities, if any, are conserved during this collision? Hint 1. When is kinetic energy conserved? Kinetic energy is conserved only in perfectly elastic collisions. ANSWER: perfectly elastic partially inelastic perfectly inelastic Correct Part C What is the speed of the block/bullet system after the collision? Express your answer in terms of , , and . Hint 1. Find the momentum after the collision What is the total momentum of the block/bullet system after the collision? Express your answer in terms of and other given quantities. ANSWER: Hint 2. Use conservation of momentum The momentum of the block/bullet system is conserved. Therefore, the momentum before the collision is the same as the momentum after the collision. Find a second expression for , this time expressed as the total momentum of the system before the collision. Express your answer in terms of and other given quantities. ANSWER: kinetic energy only momentum only kinetic energy and momentum neither momentum nor kinetic energy vi mw mb ptotal vf ptotal = (mw + mb)vf ptotal vi ptotal = mbvi ANSWER: Correct Problem 10.31 Ball 1, with a mass of 150 and traveling at 15.0 , collides head on with ball 2, which has a mass of 340 and is initially at rest. Part A What are the final velocities of each ball if the collision is perfectly elastic? Express your answer with the appropriate units. ANSWER: Correct Part B Express your answer with the appropriate units. ANSWER: Correct Part C vf = mb vi mb+mw g m/s g (vfx) = -5.82 1 ms (vfx) = 9.18 2 ms What are the final velocities of each ball if the collision is perfectly inelastic? Express your answer with the appropriate units. ANSWER: Correct Part D Express your answer with the appropriate units. ANSWER: Correct Enhanced EOC: Problem 10.43 A package of mass is released from rest at a warehouse loading dock and slides down the = 2.2 – high, frictionless chute to a waiting truck. Unfortunately, the truck driver went on a break without having removed the previous package, of mass , from the bottom of the chute. You may want to review ( pages 265 – 269) . For help with math skills, you may want to review: Solving Algebraic Equations (vfx) = 4.59 1 ms (vfx) = 4.59 2 ms m h m 2m Part A Suppose the packages stick together. What is their common speed after the collision? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem There are two parts to this problem: the block sliding down the frictionless incline and the collision. What conservation laws are valid in each part? In terms of , what are the kinetic and potential energies of the block at the top of the incline? What is the potential energy of the same block at the bottom just before the collision? What are the kinetic energy and velocity of block just before the collision? What is conserved during the collision? What is the total momentum of the two blocks before the collision? What is the momentum of the two blocks stuck together after the collision? What is the velocity of the two blocks after the collision? ANSWER: Correct Part B Suppose the collision between the packages is perfectly elastic. To what height does the package of mass rebound? Express your answer to two significant figures and include the appropriate units. Hint 1. How to approach the problem There are three parts to this problem: the block sliding down the incline, the collision, and mass going back up the incline. What conservation laws are valid in each part? m m v = 2.2 ms m m What is an elastic collision? For an elastic collision, how are the initial and final velocities related when one of the masses is initially at rest? Using the velocity of just before the collision from Part A, what is the velocity of just after the collision in this case? What are the kinetic and potential energies of mass just after the collision? What is the kinetic energy of mass at its maximum rebound height? Using conservation of energy, what is the potential energy of mass at its maximum height? What is the maximum height? ANSWER: Correct Problem 10.35 A cannon tilted up at a 35.0 angle fires a cannon ball at 79.0 from atop a 21.0 -high fortress wall. Part A What is the ball’s impact speed on the ground below? Express your answer with the appropriate units. ANSWER: Correct Problem 10.45 A 1000 safe is 2.5 above a heavy-duty spring when the rope holding the safe breaks. The safe hits the spring and compresses it 48 . m m m m m h = 24 cm $ m/s m vf = 81.6 ms kg m cm Part A What is the spring constant of the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 10.49 A 100 block on a frictionless table is firmly attached to one end of a spring with = 21 . The other end of the spring is anchored to the wall. A 30 ball is thrown horizontally toward the block with a speed of 6.0 . Part A If the collision is perfectly elastic, what is the ball’s speed immediately after the collision? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the maximum compression of the spring? Express your answer to two significant figures and include the appropriate units. ANSWER: = 2.5×105 k Nm g k N/m g m/s v = 3.2 ms Correct Part C Repeat part A for the case of a perfectly inelastic collision. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part D Repeat part B for the case of a perfectly inelastic collision. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Score Summary: Your score on this assignment is 99.4%. You received 120.28 out of a possible total of 121 points. x = 0.19 m v = 1.4 ms x = 0.11 m

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Extra Credit Due: 11:59pm on Thursday, May 15, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy A Man Running to Catch a Bus A man is running at speed (much less than the speed of light) to catch a bus already at a stop. At , when he is a distance from the door to the bus, the bus starts moving with the positive acceleration . Use a coordinate system with at the door of the stopped bus. Part A What is , the position of the man as a function of time? Answer symbolically in terms of the variables , , and . Hint 1. Which equation should you use for the man’s speed? Because the man’s speed is constant, you may use . ANSWER: Correct Part B What is , the position of the bus as a function of time? Answer symbolically in terms of and . = Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 1 of 57 5/9/2014 8:02 PM Hint 1. Which equation should you use for the bus’s acceleration? Because the bus has constant acceleration, you may use . Recall that . ANSWER: Correct Part C What condition is necessary for the man to catch the bus? Assume he catches it at time . Hint 1. How to approach this problem If the man is to catch the bus, then at some moment in time , the man must arrive at the position of the door of the bus. How would you express this condition mathematically? ANSWER: Correct Part D Inserting the formulas you found for and into the condition , you obtain the following: , or . Intuitively, the man will not catch the bus unless he is running fast enough. In mathematical terms, there is a constraint on the man’s speed so that the equation above gives a solution for that is a real positive number. Find , the minimum value of for which the man will catch the bus. Express the minimum value for the man’s speed in terms of and . = Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 2 of 57 5/9/2014 8:02 PM Hint 1. Consider the discriminant Use the quadratic equation to solve: . What is the discriminant (the part under the radical) of the solution for ? Hint 1. The quadratic formula Recall: If then ANSWER: Hint 2. What is the constraint? To get a real value for , the discriminant must be greater then or equal to zero. This condition yields a constraint that exceed . ANSWER: Correct Part E Assume that the man misses getting aboard when he first meets up with the bus. Does he get a second chance if he continues to run at the constant speed ? = = Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 3 of 57 5/9/2014 8:02 PM Hint 1. What is the general quadratic equation? The general quadratic equation is , where , , and are constants. Depending on the value of the discriminant, , the equation may have two real valued 1. solutions if , 2. one real valued solution if , or 3. two complex valued solutions if . In this case, every real valued solution corresponds to a time at which the man is at the same position as the door of the bus. ANSWER: Correct Adding and Subtracting Vectors Conceptual Question Six vectors (A to F) have the magnitudes and directions indicated in the figure. Part A Which two vectors, when added, will have the largest (positive) x component? Hint 1. Largest x component The two vectors with the largest x components will, when combined, give the resultant with the largest x component. Keep in mind that positive x components are larger than negative x components. No; there is no chance he is going to get aboard. Yes; he will get a second chance Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 4 of 57 5/9/2014 8:02 PM ANSWER: Correct Part B Which two vectors, when added, will have the largest (positive) y component? Hint 1. Largest y component The two vectors with the largest y components will, when combined, give the resultant with the largest y component. Keep in mind that positive y components are larger than negative y components. ANSWER: Correct Part C Which two vectors, when subtracted (i.e., when one vector is subtracted from the other), will have the largest magnitude? Hint 1. Subtracting vectors To subtract two vectors, add a vector with the same magnitude but opposite direction of one of the vectors to the other vector. ANSWER: C and E E and F A and F C and D B and D C and D A and F E and F A and B E and D Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 5 of 57 5/9/2014 8:02 PM Correct Tactics Box 3.1 Determining the Components of a Vector Learning Goal: To practice Tactics Box 3.1 Determining the Components of a Vector. When a vector is decomposed into component vectors and parallel to the coordinate axes, we can describe each component vector with a single number (a scalar) called the component. This tactics box describes how to determine the x component and y component of vector , denoted and . TACTICS BOX 3.1 Determining the components of a vector The absolute value of the x component is the magnitude of the 1. component vector . The sign of is positive if points in the positive x direction; it is negative if points in the negative x direction. 2. 3. The y component is determined similarly. Part A What is the magnitude of the component vector shown in the figure? Express your answer in meters to one significant figure. ANSWER: A and F A and E D and B C and D E and F Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 6 of 57 5/9/2014 8:02 PM Correct Part B What is the sign of the y component of vector shown in the figure? ANSWER: Correct Part C Now, combine the information given in the tactics box above to find the x and y components, and , of vector shown in the figure. Express your answers, separated by a comma, in meters to one significant figure. = 5 positive negative Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 7 of 57 5/9/2014 8:02 PM ANSWER: Correct Conceptual Problem about Projectile Motion Learning Goal: To understand projectile motion by considering horizontal constant velocity motion and vertical constant acceleration motion independently. Projectile motion refers to the motion of unpowered objects (called projectiles) such as balls or stones moving near the surface of the earth under the influence of the earth’s gravity alone. In this analysis we assume that air resistance can be neglected. An object undergoing projectile motion near the surface of the earth obeys the following rules: An object undergoing projectile motion travels horizontally at a constant rate. That is, the x component of its velocity, , is constant. 1. An object undergoing projectile motion moves vertically with a constant downward acceleration whose magnitude, denoted by , is equal to 9.80 near the surface of the earth. Hence, the y component of its velocity, , changes continuously. 2. An object undergoing projectile motion will undergo the horizontal and vertical motions described above from the instant it is launched until the instant it strikes the ground again. Even though the horizontal and vertical motions can be treated independently, they are related by the fact that they occur for exactly the same amount of time, namely the time the projectile is in the air. 3. The figure shows the trajectory (i.e., the path) of a ball undergoing projectile motion over level ground. The time corresponds to the moment just after the ball is launched from position and . Its launch velocity, also called the initial velocity, is . Two other points along the trajectory are indicated in the figure. One is the moment the ball reaches the peak of its trajectory, at time with velocity . Its position at this moment is denoted by or since it is at its maximum height. The other point, at time with velocity , corresponds to the moment just before the ball strikes the ground on the way back down. At this time its position is , also known as ( since it is at its maximum horizontal range. Projectile motion is symmetric about the peak, provided the object lands at the same vertical height from which is was launched, as is the case here. Hence . Part A , = -2,-5 , Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 8 of 57 5/9/2014 8:02 PM How do the speeds , , and (at times ,

Extra Credit Due: 11:59pm on Thursday, May 15, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy A Man Running to Catch a Bus A man is running at speed (much less than the speed of light) to catch a bus already at a stop. At , when he is a distance from the door to the bus, the bus starts moving with the positive acceleration . Use a coordinate system with at the door of the stopped bus. Part A What is , the position of the man as a function of time? Answer symbolically in terms of the variables , , and . Hint 1. Which equation should you use for the man’s speed? Because the man’s speed is constant, you may use . ANSWER: Correct Part B What is , the position of the bus as a function of time? Answer symbolically in terms of and . = Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 1 of 57 5/9/2014 8:02 PM Hint 1. Which equation should you use for the bus’s acceleration? Because the bus has constant acceleration, you may use . Recall that . ANSWER: Correct Part C What condition is necessary for the man to catch the bus? Assume he catches it at time . Hint 1. How to approach this problem If the man is to catch the bus, then at some moment in time , the man must arrive at the position of the door of the bus. How would you express this condition mathematically? ANSWER: Correct Part D Inserting the formulas you found for and into the condition , you obtain the following: , or . Intuitively, the man will not catch the bus unless he is running fast enough. In mathematical terms, there is a constraint on the man’s speed so that the equation above gives a solution for that is a real positive number. Find , the minimum value of for which the man will catch the bus. Express the minimum value for the man’s speed in terms of and . = Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 2 of 57 5/9/2014 8:02 PM Hint 1. Consider the discriminant Use the quadratic equation to solve: . What is the discriminant (the part under the radical) of the solution for ? Hint 1. The quadratic formula Recall: If then ANSWER: Hint 2. What is the constraint? To get a real value for , the discriminant must be greater then or equal to zero. This condition yields a constraint that exceed . ANSWER: Correct Part E Assume that the man misses getting aboard when he first meets up with the bus. Does he get a second chance if he continues to run at the constant speed ? = = Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 3 of 57 5/9/2014 8:02 PM Hint 1. What is the general quadratic equation? The general quadratic equation is , where , , and are constants. Depending on the value of the discriminant, , the equation may have two real valued 1. solutions if , 2. one real valued solution if , or 3. two complex valued solutions if . In this case, every real valued solution corresponds to a time at which the man is at the same position as the door of the bus. ANSWER: Correct Adding and Subtracting Vectors Conceptual Question Six vectors (A to F) have the magnitudes and directions indicated in the figure. Part A Which two vectors, when added, will have the largest (positive) x component? Hint 1. Largest x component The two vectors with the largest x components will, when combined, give the resultant with the largest x component. Keep in mind that positive x components are larger than negative x components. No; there is no chance he is going to get aboard. Yes; he will get a second chance Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 4 of 57 5/9/2014 8:02 PM ANSWER: Correct Part B Which two vectors, when added, will have the largest (positive) y component? Hint 1. Largest y component The two vectors with the largest y components will, when combined, give the resultant with the largest y component. Keep in mind that positive y components are larger than negative y components. ANSWER: Correct Part C Which two vectors, when subtracted (i.e., when one vector is subtracted from the other), will have the largest magnitude? Hint 1. Subtracting vectors To subtract two vectors, add a vector with the same magnitude but opposite direction of one of the vectors to the other vector. ANSWER: C and E E and F A and F C and D B and D C and D A and F E and F A and B E and D Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 5 of 57 5/9/2014 8:02 PM Correct Tactics Box 3.1 Determining the Components of a Vector Learning Goal: To practice Tactics Box 3.1 Determining the Components of a Vector. When a vector is decomposed into component vectors and parallel to the coordinate axes, we can describe each component vector with a single number (a scalar) called the component. This tactics box describes how to determine the x component and y component of vector , denoted and . TACTICS BOX 3.1 Determining the components of a vector The absolute value of the x component is the magnitude of the 1. component vector . The sign of is positive if points in the positive x direction; it is negative if points in the negative x direction. 2. 3. The y component is determined similarly. Part A What is the magnitude of the component vector shown in the figure? Express your answer in meters to one significant figure. ANSWER: A and F A and E D and B C and D E and F Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 6 of 57 5/9/2014 8:02 PM Correct Part B What is the sign of the y component of vector shown in the figure? ANSWER: Correct Part C Now, combine the information given in the tactics box above to find the x and y components, and , of vector shown in the figure. Express your answers, separated by a comma, in meters to one significant figure. = 5 positive negative Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 7 of 57 5/9/2014 8:02 PM ANSWER: Correct Conceptual Problem about Projectile Motion Learning Goal: To understand projectile motion by considering horizontal constant velocity motion and vertical constant acceleration motion independently. Projectile motion refers to the motion of unpowered objects (called projectiles) such as balls or stones moving near the surface of the earth under the influence of the earth’s gravity alone. In this analysis we assume that air resistance can be neglected. An object undergoing projectile motion near the surface of the earth obeys the following rules: An object undergoing projectile motion travels horizontally at a constant rate. That is, the x component of its velocity, , is constant. 1. An object undergoing projectile motion moves vertically with a constant downward acceleration whose magnitude, denoted by , is equal to 9.80 near the surface of the earth. Hence, the y component of its velocity, , changes continuously. 2. An object undergoing projectile motion will undergo the horizontal and vertical motions described above from the instant it is launched until the instant it strikes the ground again. Even though the horizontal and vertical motions can be treated independently, they are related by the fact that they occur for exactly the same amount of time, namely the time the projectile is in the air. 3. The figure shows the trajectory (i.e., the path) of a ball undergoing projectile motion over level ground. The time corresponds to the moment just after the ball is launched from position and . Its launch velocity, also called the initial velocity, is . Two other points along the trajectory are indicated in the figure. One is the moment the ball reaches the peak of its trajectory, at time with velocity . Its position at this moment is denoted by or since it is at its maximum height. The other point, at time with velocity , corresponds to the moment just before the ball strikes the ground on the way back down. At this time its position is , also known as ( since it is at its maximum horizontal range. Projectile motion is symmetric about the peak, provided the object lands at the same vertical height from which is was launched, as is the case here. Hence . Part A , = -2,-5 , Extra Credit http://session.masteringphysics.com/myct/assignmentPrintView?displayM… 8 of 57 5/9/2014 8:02 PM How do the speeds , , and (at times ,

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Lectorial 5: The Gravitron The Gravitron (shown in figure 1 [1]) is a carnival ride designed to simulate the experience of zero gravity. The ride consists of a 15 metre diameter circular chamber which spins around a centre shaft. The spinning motion applies a force to the occupants of the ride pinning them up against their seat. Figure 1: The Gravitron carnival ride. For this lectorial task we want to study the forces being applied to the ride’s occupants and determine the g-forces they would be experiencing. According to physics, the rules for uniform circular motion are: where: 1. If the ride has a maximum rotational speed of 24 revolutions per minute (rpm), determine the force being applied to the ride’s occupants. What gforces are the people experiencing (assume occupants are 65 kg adults)? [1] “Gravitron” used under Creative Commons licence (https://creativecommons.org/licenses/by-nc-sa/2.0/). Photo by: bobdole369 Newtons 2 r v F = ma = m angular speed in radians per second rotational speed in revolutions per second (or Hz) radius of the Gravitron tangential velocity of the Gravitron mass of occupant = = = = = w f r v m -1 v = wr ms w = 2pf rad/sec Typically the Gravitron ride takes approximately 20 seconds to reach its maximum rotational speed of 24 rpms and the whole ride lasts for around 80 seconds. This means the ride’s occupants are exposed to non-uniform circular motion meaning there is changing linear velocity at certain parts of the ride. For non-uniform circular motion the following formulae are useful: where: A GPS tracking device was attached to a person in the Gravitron and data was obtained about their x,y displacement vs. time over the 80 second duration of the ride. The data was saved in a .csv file called ‘gravitron.csv.’ This file contains three columns: time, x-displacement and y-displacement, e.g.: Time, sec x-displacement y-displacement 0.00 0.10 0.20 … 2. Download this .csv file from Blackboard. Find the g-forces being applied to the ride’s occupants for the whole 80 second duration of the ride. Again assume the occupants are 65 kg adults. Think about how you could effectively present these results. -2 2 ms r v -1 a = 2 2 ms     +     = dt dy dt dx v centripetal acceleration time in seconds displacement in y direction displacement in x direction = = = = a t y x

Lectorial 5: The Gravitron The Gravitron (shown in figure 1 [1]) is a carnival ride designed to simulate the experience of zero gravity. The ride consists of a 15 metre diameter circular chamber which spins around a centre shaft. The spinning motion applies a force to the occupants of the ride pinning them up against their seat. Figure 1: The Gravitron carnival ride. For this lectorial task we want to study the forces being applied to the ride’s occupants and determine the g-forces they would be experiencing. According to physics, the rules for uniform circular motion are: where: 1. If the ride has a maximum rotational speed of 24 revolutions per minute (rpm), determine the force being applied to the ride’s occupants. What gforces are the people experiencing (assume occupants are 65 kg adults)? [1] “Gravitron” used under Creative Commons licence (https://creativecommons.org/licenses/by-nc-sa/2.0/). Photo by: bobdole369 Newtons 2 r v F = ma = m angular speed in radians per second rotational speed in revolutions per second (or Hz) radius of the Gravitron tangential velocity of the Gravitron mass of occupant = = = = = w f r v m -1 v = wr ms w = 2pf rad/sec Typically the Gravitron ride takes approximately 20 seconds to reach its maximum rotational speed of 24 rpms and the whole ride lasts for around 80 seconds. This means the ride’s occupants are exposed to non-uniform circular motion meaning there is changing linear velocity at certain parts of the ride. For non-uniform circular motion the following formulae are useful: where: A GPS tracking device was attached to a person in the Gravitron and data was obtained about their x,y displacement vs. time over the 80 second duration of the ride. The data was saved in a .csv file called ‘gravitron.csv.’ This file contains three columns: time, x-displacement and y-displacement, e.g.: Time, sec x-displacement y-displacement 0.00 0.10 0.20 … 2. Download this .csv file from Blackboard. Find the g-forces being applied to the ride’s occupants for the whole 80 second duration of the ride. Again assume the occupants are 65 kg adults. Think about how you could effectively present these results. -2 2 ms r v -1 a = 2 2 ms     +     = dt dy dt dx v centripetal acceleration time in seconds displacement in y direction displacement in x direction = = = = a t y x

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Sample to sample: A researcher suspected that students who study with music playing in the background would not retain information as well as students who study under quiet conditions. To test her hypothesis, she randomly assigned 18 participants to either a music or quiet study condition and had them study the same information for the same amount of time. She then administered a 10 item test on the material to all participants. The test scores were interval/ratio data and normally distributed. Assume alpha=.05. Their scores were as follows: Music group: 6, 5, 6, 5, 6, 6, 7, 8, 5 Quiet group: 10, 9, 8, 7, 9, 6, 8, 6, 9 – – Describe what type of decision maker you are. Talk about a time you had to make a decision that affected others and what was the process in which you reached that decision. Be specific. Write your reaction to a club meeting that you have attended. Discuss how you felt about being at the meeting, how the meeting was run, what leadership characteristics did the officers exhibit, etc.? Was the meeting effective? Solving the water scarcity problem to achieve long-term water availability lake chad

Sample to sample: A researcher suspected that students who study with music playing in the background would not retain information as well as students who study under quiet conditions. To test her hypothesis, she randomly assigned 18 participants to either a music or quiet study condition and had them study the same information for the same amount of time. She then administered a 10 item test on the material to all participants. The test scores were interval/ratio data and normally distributed. Assume alpha=.05. Their scores were as follows: Music group: 6, 5, 6, 5, 6, 6, 7, 8, 5 Quiet group: 10, 9, 8, 7, 9, 6, 8, 6, 9 – – Describe what type of decision maker you are. Talk about a time you had to make a decision that affected others and what was the process in which you reached that decision. Be specific. Write your reaction to a club meeting that you have attended. Discuss how you felt about being at the meeting, how the meeting was run, what leadership characteristics did the officers exhibit, etc.? Was the meeting effective? Solving the water scarcity problem to achieve long-term water availability lake chad

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ELEC 2000 Semiconductor Devices Homework #1 Choose the answer that best completes the statement or answers the question. (1) Assume the valence electron is removed from a copper atom. The net charge of the atom becomes a. 0 b. +1 c. -1 d. +4 (2) The valence electron of a copper atom experiences what kind of attraction toward the nucleus? a. None b. Weak c. Strong d. Impossible to say (3) How many valence electrons does a silicon atom have? a. 0 b. 1 c. 2 d. 4 (4) Silicon atoms combine into an orderly pattern called a a. Covalent bond b. Crystal c. Semiconductor d. Valence orbit (5) An intrinsic semiconductor has some holes in it at room temperature. What causes these holes? a. Doping b. Free electrons c. Thermal energy d. Valence electrons (6) The merging of a free electron and a hole is called a. Covalent bonding b. Lifetime c. Recombination d. Thermal energy (7) At room temperature an intrinsic silicon crystal acts approximately a. A Battery b. A conductor c. An insulator d. Copper wire (8) The amount of time between the creation of a hole and its disappearance is called a. Doping b. Lifetime c. Recombination d. Valence (9) A conductor has how many type of flow? a. 1 b. 2 c. 3 d. 4 (10) A semiconductor has how many types of flow? a. 1 b. 2 c. 3 d. 4 (11) For semiconductor material, its valence orbit is saturated when it contains a. 1 electron b. Equal (+) and (-) ions c. 4 electrons d. 8 electrons (12) In an intrinsic semiconductor, the number of holes a. Equal the number of free electrons b. Is greater than the number of free electrons c. Is less than the number of free electrons d. None of the above (13) The number of free electrons and holes in an intrinsic semiconductor decreases when the temperature a. Decreases b. Increases c. Stays the same d. None of the above (14) The flow of valence electrons to the right means that holes are flowing to the a. Left b. Right c. Either way d. None of the above (15) Holes act like a. Atoms b. Crystals c. Negative charges d. Positive charges (16) An donor atom has how many valence electrons? a. 1 b. 3 c. 4 d. 5 (17) If you wanted to produce a p-type semiconductor, which of these would you use? a. Acceptor atoms b. Donor atoms c. Pentavalent impurity d. Silicon (18) Electrons are the minority carriers in which type of semiconductor? a. Extrinsic b. Intrinsic c. n-Type d. p-type (19) Silver is the best conductor. How many valence electrons do you think it has? a. 1 b. 4 c. 18 d. 29 (20) Which of the following describes an n-type semiconductor? a. Neutral b. Positively charged c. Negatively charged d. has many holes (21) What is the barrier potential of a silicon diode a room temperature? a. 0.3 V b. 0.7 V c. 1 V d. 2 mV per degree Celsius

ELEC 2000 Semiconductor Devices Homework #1 Choose the answer that best completes the statement or answers the question. (1) Assume the valence electron is removed from a copper atom. The net charge of the atom becomes a. 0 b. +1 c. -1 d. +4 (2) The valence electron of a copper atom experiences what kind of attraction toward the nucleus? a. None b. Weak c. Strong d. Impossible to say (3) How many valence electrons does a silicon atom have? a. 0 b. 1 c. 2 d. 4 (4) Silicon atoms combine into an orderly pattern called a a. Covalent bond b. Crystal c. Semiconductor d. Valence orbit (5) An intrinsic semiconductor has some holes in it at room temperature. What causes these holes? a. Doping b. Free electrons c. Thermal energy d. Valence electrons (6) The merging of a free electron and a hole is called a. Covalent bonding b. Lifetime c. Recombination d. Thermal energy (7) At room temperature an intrinsic silicon crystal acts approximately a. A Battery b. A conductor c. An insulator d. Copper wire (8) The amount of time between the creation of a hole and its disappearance is called a. Doping b. Lifetime c. Recombination d. Valence (9) A conductor has how many type of flow? a. 1 b. 2 c. 3 d. 4 (10) A semiconductor has how many types of flow? a. 1 b. 2 c. 3 d. 4 (11) For semiconductor material, its valence orbit is saturated when it contains a. 1 electron b. Equal (+) and (-) ions c. 4 electrons d. 8 electrons (12) In an intrinsic semiconductor, the number of holes a. Equal the number of free electrons b. Is greater than the number of free electrons c. Is less than the number of free electrons d. None of the above (13) The number of free electrons and holes in an intrinsic semiconductor decreases when the temperature a. Decreases b. Increases c. Stays the same d. None of the above (14) The flow of valence electrons to the right means that holes are flowing to the a. Left b. Right c. Either way d. None of the above (15) Holes act like a. Atoms b. Crystals c. Negative charges d. Positive charges (16) An donor atom has how many valence electrons? a. 1 b. 3 c. 4 d. 5 (17) If you wanted to produce a p-type semiconductor, which of these would you use? a. Acceptor atoms b. Donor atoms c. Pentavalent impurity d. Silicon (18) Electrons are the minority carriers in which type of semiconductor? a. Extrinsic b. Intrinsic c. n-Type d. p-type (19) Silver is the best conductor. How many valence electrons do you think it has? a. 1 b. 4 c. 18 d. 29 (20) Which of the following describes an n-type semiconductor? a. Neutral b. Positively charged c. Negatively charged d. has many holes (21) What is the barrier potential of a silicon diode a room temperature? a. 0.3 V b. 0.7 V c. 1 V d. 2 mV per degree Celsius

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