Energy Freedman

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A) the same B) twice as greatC) one-half as great D) four times as great

1. The diagram below shows block A, having mass 2m andspeed v, and block B having mass m and speed 2v.

Compared to the kinetic energy of block A, the kineticenergy of block B is

A) velocity B) momentumC) displacement D) kinetic energy

2. If the direction of a moving car changes and its speedremains constant, which quantity must remain the same?

A) 5.66 m/s B) 8.00 m/sC) 32.0 m/s D) 64.0 m/s

3. A 60.0-kilogram runner has 1920 joules of kinetic energy.At what speed is she running?

A) 240. J B) 480. JC) 1440 J D) 1920 J

4. A 45.0-kilogram boy is riding a 15.0-kilogram bicycle witha speed of 8.00 meters per second. What is the combinedkinetic energy of the boy and the bicycle?

A) quadrupled B) quarteredC) doubled D) halved

5. If the speed of a car is doubled, the kinetic energy of the caris

A)

B)

C)

D)

6. Which graph best represents the relationship between thekinetic energy, KE, and the velocity of an object acceleratingin a straight line?

A) one-fourth as great B) one-half as greatC) the same D) four times as great

7. A 1.0-kilogram rubber ball traveling east at 4.0 meters persecond hits a wall and bounces back toward the west at 2.0meters per second. Compared to the kinetic energy of theball before it hits the wall, the kinetic energy of the ballafter it bounces off the wall is

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A)

B)

C)

D)

8. A 1.0-kilogram book resting on the ground is moved 1.0meter at various angles relative to the horizontal. In whichdirection does the 1.0-meter displacement produce thegreatest increase in the book’s gravitational potentialenergy?

A) 2.17 104 J B) 2.21 103 JC) 2.25 102 J D) 2.29 101 J

9. What is the gravitational potential energy with respect to thesurface of the water of a 75.0 kilogram diver located 3.00meters above the water?

A) 310 J B) 32 J C) 3.3 J D) 0.34 J

10. An object weighing 15 Newtons is lifted from the groundto a height of 0.22 meter. The increase in the object’sgravitational potential energy is approximately

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A) B)

C) D)

11. Which graph best represents the relationship between the gravitational potential energy of a freely falling objectand the object’s height above the ground near the surface of Earth?

A) less B) greaterC) the same

12. Two weightlifters, one 1.5 meters tall and one 2.0 meterstall, raise identical 50.-kilogram masses above their heads.Compared to the work done by the weightlifter who is 1.5meters tall, the work done by the weightlifter who is 2.0meters tall is

A) 20. N B) 15 N C) 12 N D) 4.0 N

13. A student does 60. joules of work pushing a 3.0-kilogrambox up the full length of a ramp that is 5.0 meters long.What is the magnitude of the force applied to the box to dothis work?

A) W would remain the same and the magnitude of F would decrease.

B) W would remain the same and the magnitude of F would increase.

C) W would increase and the magnitude of F woulddecrease.

D) W would increase and the magnitude of F wouldincrease.

14. The diagram below shows a 50.-kilogram crate on africtionless plane at angle to the horizontal. The crate ispushed at constant speed up the incline from point A topoint B by force F.

If angle were increased, what would be the effect on themagnitude of force F and the total work W done on thecrate as it is moved from A to B?

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A) 100. J B) 200. J C) 173 J D) 273 J

15. The diagram below shows points A, B, and C at or nearEarth's surface. As a mass is moved from A to B, 100.joules of work are done against gravity.

What is the amount of work done against gravity as anidentical mass is moved from A to C?

A) 2.0 × 104J B) 3.8 × 104JC) 2.0 × 106 J D) 3.8 × 106 J

16. A constant force of 1900 Newtons is required to keep anautomobile having a mass of 1.0 × 103 kilograms movingat a constant speed of 20. meters per second. The workdone in moving the automobile a distance of 2.0 × 103

meters is

A) newton • secondmeter

B) newton • metersecond

C) newton/meterD) newton • meter

17. Which combination of units can be used to express work?

A) 100. J B) 200. J C) 150. J D) 40.0 J

18. In the diagram below, a 20.0-newton force is used to pusha 2.00-kilogram cart a distance of 5.00 meters.

The work done on the cart is

A) 80. J B) 120 J C) 240 J D) 480 J

19. A student applies a 20.-newton force to move a crate at aconstant speed of 4.0 meters per second across a roughfloor. How much work is done by the student on the cratein 6.0 seconds?

A) 29 W B) 280 WC) 1.4 × 103 W D) 1.4 × 104 W

20. A 40.-kilogram student runs up a staircase to a floor that is5.0 meters higher than her starting point in 7.0 seconds.The student’s power output is

A) impulse B) momentumC) speed D) power

21. The graph below represents the relationship between thework done by a student running up a flight of stairs and thetime of ascent.

What does the slope of this graph represent?

A) 5.0 N B) 20. N C) 40. N D) 50. N

22. In raising an object vertically at a constant speed of 2.0meters per second, 10. watts of power is developed. Theweight of the object is

A) 2 × 103 m/s B) 50 m/sC) 5 m/s D) 0.2 m/s

23. A 2000-watt motor working at full capacity can verticallylift a 400-newton weight at a constant speed of

A) 2.5 × 10–2 J B) 4.0 × 101 WC) 7.5 × 103 J D) 9.0 × 103 W

24. A boat weighing 9.0 × 102 Newtons requires a horizontalforce of 6.0 × 102 Newtons to move it across the water at1.5 × 101 meters per second. The boat’s engine mustprovide energy at the rate of

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A) 1.3 × 102 W B) 3.8 × 102 WC) 1.2 × 103 W D) 3.7 × 103 W

25. A 95-kilogram student climbs 4.0 meters up a rope in 3.0seconds. What is the power output of the student?

A) 1.6 m B) 8.0 m C) 40. m D) 360 m

26. A motor used 120. watts of power to raise a 15-newtonobject in 5.0 seconds. Through what vertical distance wasthe object raised?

A) 24 W B) 32 W C) 48 W D) 96 W

27. A 3.0-kilogram block is initially at rest on a frictionless,horizontal surface. The block is moved 8.0 meters in 2.0seconds by the application of a 12-newton horizontalforce, as shown in the diagram below.

What is the average power developed while moving theblock?

A) 0.500 s B) 2.00 sC) 5.00 s D) 50.0 s

28. A motor having a power rating of 500. watts is used to liftan object weighing 100. Newtons. How much time doesthe motor take to lift the object a vertical distance of 10.0meters?

A) 0.67 m B) 1.5 mC) 6.0 m D) 24 m

29. What is the maximum height to which a 1200-watt motorcould lift an object weighing 200. Newtons in 4.0 seconds?

A) 2.6 m B) 5.1 m C) 13 m D) 25 m

30. A 0.50-kilogram ball is thrown vertically upward with aninitial kinetic energy of 25 joules. Approximately howhigh will the ball rise? [Neglect air resistance.]

A) 4.91 J B) 50.0 J C) 250. J D) 491 J

31. The diagram below shows a moving, 5.00-kilogram cart atthe foot of a hill 10.0 meters high. For the cart to reach thetop of the hill, what is the minimum kinetic energy of thecart in the position shown? [Neglect energy loss due tofriction.]

A) 20 J B) 200 J C) 700 J D) 900 J

32. A 1-kilogram rock is dropped from a cliff 90 meters high.After falling 20 meters, the kinetic energy of the rock isapproximately

A) decreases B) increasesC) remains the same

33. As a ball falls freely (without friction) toward the ground,its total mechanical energy

A) decreases B) increasesC) remains the same

34. As an object falls freely, the kinetic energy of the object

A) generator B) motorC) transformer D) mass spectrometer

35. Which device transforms mechanical energy into electricalenergy?

A) exactly the same B) 330 J lessC) 330 J more D) 150 J more

36. As shown in the diagram below, a student exerts anaverage force of 600. newtons on a rope to lift a50.0-kilogram crate a vertical distance of 3.00 meters.

Compared to the work done by the student, thegravitational potential energy gained by the crate is

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A) weight B) momentumC) potential energy D) internal energy

37. When a force moves an object over a rough, horizontalsurface at a constant velocity, the work done againstfriction produces an increase in the object’s

A) gravitational potential energy, onlyB) internal energy, onlyC) gravitational potential energy and kinetic energyD) internal energy and kinetic energy

38. A constant force is used to keep a block sliding at constantvelocity along a rough horizontal track. As the blockslides, there could be an increase in its

A) 1.0 J B) 0.0 J C) 3.0 J D) 7.0 J

39. A block weighing 15 Newtons is pulled to the top of anincline that is 0.20 meter above the ground, as shownbelow.

If 4.0 joules of work are needed to pull the block the fulllength of the incline, how much work is done againstfriction? A) 40. J B) 360 J C) 400. J D) 760 J

40. In the diagram below, 400. joules of work is done raising a72-newton weight a vertical distance of 5.0 meters.

How much work is done to overcome friction as theweight is raised?

A) 0 J B) 8 J C) 45 J D) 90. J

41. The diagram below shows a 5.0-kilogram mass sliding 9.0meters down an incline from a height of 2.0 meters in 3.0seconds. The object gains 90. joules of kinetic energywhile sliding.

How much work is done against friction as the mass slidesthe 9.0 meters?

A) 3.75 J B) 7.50 J C) 15.0 J D) 30.0 J

42. When a 1.53-kilogram mass is placed on a spring with aspring constant of 30.0 newtons per meter, the spring iscompressed 0.500 meter. How much energy is stored inthe spring?

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A) 3.2 × 105 N/m B) 4.0 × 103 N/mC) 2.5 N/m D) 3.1 × 10–2 N/m

43. The spring in a scale in the produce department of asupermarket stretches 0.025 meter when a watermelonweighing 1.0 × 102 newtons is placed on the scale. Thespring constant for this spring is

A) 30. N/m B) 60. N/mC) 120 N/m D) 240 N/m

44. As shown in the diagram below, a 0.50-meter-long springis stretched from its equilibrium position to a length of1.00 meter by a weight.

If 15 joules of energy are stored in the stretched spring,what is the value of the spring constant?

A) 1 J B) 0.5 J C) 0.2 J D) 0.1 J

45. A 5-newton force causes a spring to stretch 0.2 meter.What is the potential energy stored in the stretched spring?

A) smaller B) largerC) the same

46. The graph below shows elongation as a function of theapplied force for two springs, A and B.

Compared to the spring constant for spring A, the springconstant for spring B is

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A) B)

C) D)

47. Which graph best represents the elastic potential energy stored in a spring (PEs) as a function of its elongation, x?

A) 0.020 N/m B) 2.0 N/mC) 25 N/m D) 50. N/m

48. The graph below shows the relationship between theelongation of a spring and the force applied to the springcausing it to stretch.

What is the spring constant for this spring?

A) 2.4 J B) 4.8 J C) 12 J D) 24 J

49. A spring has a spring constant of 120 newtons per meter.How much potential energy is stored in the spring as it isstretched 0.20 meter?

A) 0.068 J B) 0.14 JC) 3.4 J D) 6.8 J

50. In the diagram below, a student compresses the spring in apop-up toy 0.020 meter.

If the spring has a spring constant of 340 newtons permeter, how much energy is being stored in the spring?

A) 10 N/m B) 40 N/mC) 100 N/m D) 400 N/m

51. The diagram below shows a 0.1-kilogram apple attached toa branch of a tree 2 meters above a spring on the groundbelow.

The apple falls and hits the spring, compressing it 0.1meter from its rest position. If all of the gravitationalpotential energy of the apple on the tree is transferred tothe spring when it is compressed, what is the springconstant of this spring?

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A) 1.9 J B) 7.5 J C) 30. J D) 56 J

52. The spring of a toy car is wound by pushing the carbackward with an average force of 15 Newtons through adistance of 0.50 meter. How much elastic potential energyis stored in the car’s spring during this process?

A) 1.3 × 103 J B) 2.0 × 104 JC) 2.5 × 103 J D) 1.0 × 104 J

53. A catapult with a spring constant of 1.0 × 104 newtons permeter is required to launch an airplane from the deck of anaircraft carrier. The plane is released when it has beendisplaced 0.50 meter from its equilibrium position by thecatapult. The energy acquired by the airplane from thecatapult during takeoff is approximately

A) 0.080 J B) 0.20 JC) 0.30 J D) 0.78 J

54. A 0.10-kilogram ball dropped vertically from a height ofl.00 meter above the floor bounces back to a height of 0.80meter. The mechanical energy lost by the ball as itbounces is

A) The potential energy at A equals the kinetic energy atC.

B) The speed of the pendulum at A equals the speed ofthe pendulum at B.

C) The potential energy at B equals the potential energyat C.

D) The potential energy at A equals the kineticenergy at B.

55. The diagram below shows three positions, A, B, and C, inthe swing of a pendulum, released from rest at point A.[Neglect friction.]

Which statement is true about this swinging pendulum?

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Base your answers to questions 56 and 57 on the information and diagram below.

A -kilogram car is initially at rest at point A on a roller coaster track. The car carries a -kilogrampassenger and is meters above the ground at point . [Neglect friction.]

56. Calculate the total gravitational potential energy, relative to the ground, of the car and the passenger at point .[Show all work, including the equation and substitution with units.]

57. Calculate the speed of the car and passenger at point . [Show all work, including the equation and substitutionwith units.]

Base your answers to questions 58 through 60 on the information and diagram below.

A 1000.-kilogram empty cart moving with a speed of 6.0 meters per second is about to collide with astationary loaded cart having a total mass of 5000. kilograms, as shown. After the collision, the carts lockand move together. [Assume friction is negligible.]

58. Calculate the speed of the combined carts after the collision.

59. Calculate the kinetic energy of the combined carts after the collision.

60. How does the kinetic energy of the combined carts after the collision compare to the kinetic energy of the cartsbefore the collision?

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Base your answers to questions 61 through 63 on theinformation below.

The driver of a car made an emergency stop on astraight horizontal road. The wheels locked and thecar skidded to a stop. The marks made by the rubbertires on the dry asphalt are 16 meters long, and thecar’s mass is 1200 kilograms.

61. Calculate the magnitude of the frictional force the roadapplied to the car in stopping it.

62. Calculate the work done by the frictional force in stoppingthe car.

63. Assuming that energy is conserved, calculate the speed ofthe car before the brakes were applied.

64. Base your answer to the following question on theinformation below.

A proton starts from rest and gains joule of kinetic energy as it accelerates between pointsA and B in an electric field.

A) 7.07 × 106 m/s B) 1.00 × 107 m/sC) 4.28 × 108 m/s D) 5.00 × 1013 m/s

What is the final speed of the proton?

Base your answers to questions 65 through 67 on theinformation and diagram below.

A mass, M, is hung from a spring and reachesequilibrium at position B. The mass is then raised toposition A and released. The mass oscillates betweenpositions A and C. [Neglect friction.]

65. At which position, A, B, or C, is mass M located when thekinetic energy of the system is at a maximum? Explainyour choice.

66. At which position, A, B, or C, is mass M located when thegravitational potential energy of the system is at amaximum? Explain your choice.

67. At which position, A, B, or C, is mass M located when theelastic potential energy of the system is at a maximum?Explain your choice.

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Base your answers to questions 68 and 69 on theinformation and diagram below.

A 160.-newton box sits on a 10.-meter-longfrictionless plane inclined at an angle of 30.° to thehorizontal as shown. Force (F) applied to a ropeattached to the box causes the box to move with aconstant speed up the incline.

68. On the diagram above, construct a vector to represent theweight of the box. Use a metric ruler and a scale of 1.0centimeter = 40. newtons. Begin the vector at point B andlabel its magnitude in newtons.

69. Calculate the amount of work done in moving the boxfrom the bottom to the top of the inclined plane. [Show allwork, including the equation and substitution with units.]

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Base your answers to questions 70 and 71 on the information and diagram below.

A block of mass m starts from rest at height h on a frictionless incline. The block slides down theincline across a frictionless level surface and comes to rest by compressing a spring throughdistance x, as shown in the diagram below.

70. Name the forms of mechanical energy possessed by the system when the block is in position A and in position B.

71. Determine the spring constant, k, in terms of g, h, m, and x. [Show all work including formulas and an algebraicsolution for k.]

Base your answers to questions 72 and 73 on the information below.

A student conducted a series of experiments to investigate the effect of mass, length, andamplitude (angle of release) on a simple pendulum. The table below shows the initial conditionsfor a series of trials.

72. Which three trials should the student use to test the effect of mass on the period of the pendulum?

73. Which three trials should the student use to test the effect of length on the period of the pendulum?

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Base your answers to questions 74 and 75 on the information below.

A 680-newton student runs up a flight of stairs 3.5 meters high in 11.4 seconds. The student takes 8.5seconds to run up the same flight of stairs during a second trial.

74. Determine the power developed by the student during the 11.4 -second climb.

75. Using one or more complete sentences, compare the power developed by the student climbing the stairs in 11.4seconds to the power developed during the 8.5-second trial.

Base your answers to questions 76 through 78 on the information and the diagram below, which is drawn to ascale of 1.0 centimeter = 3.0 meters.

A 650-kilogram roller coaster car starts from rest at the top of the first hill of its track and glides freely.[Neglect friction.]

76. Using a metric ruler and the scale of 1.0 cm = 3.0 m, determine the height of the first hill.

77. Determine the gravitational potential energy of the car at the top of the first hill. [Show all calculations, includingthe equation and substitution with units.]

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78. Using one or more complete sentences, compare the kinetic energy of the car at the top of the second hill to itskinetic energy at the top of the third hill.

Base your answers to questions 79 through 81 on the information and diagram below.

A 20.-kilogram block is placed at the top of a 10.-meter-long inclined plane. The block startsfrom rest and slides without friction down the length of the incline.

79. Determine the gravitational potential energy of the block at the top of the incline. [Show all calculations,including the equation and substitution with units.]

80. Determine the kinetic energy of the block just as it reaches the bottom of the incline.

81. On the axes provided above, sketch a graph of the gravitational potential energy of the block as a function of itskinetic energy for the complete slide. Label your graph with appropriate values and units.

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Answer Key2015-16 Energy

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1. B

2. D

3. B

4. D

5. A

6. D

7. A

8. D

9. B

10. C

11. A

12. B

13. C

14. D

15. A

16. D

17. D

18. A

19. D

20. B

21. D

22. A

23. C

24. D

25. C

26. C

27. C

28. B

29. D

30. B

31. D

32. B

33. C

34. B

35. A

36. B

37. D

38. B

39. A

40. A

41. B

42. A

43. B

44. C

45. B

46. B

47. D

48. D

49. A

50. A

51. D

52. B

53. A

54. B

55. D

56.

57.

58. v f = 1.0 m/s59. KE = 3.0 x 103 J

60. The KE of thecombined cartsafter the collision isless than the KE ofthe carts before thecollision.

61. Ff = 8,000 N or8,040 N

62. W = 1.3 × 105 J or128,000 J

63. v = 15 m/s or vi =14.6 m/s

64. B

65. B, because the masshas the greatestspeed orB, because the totalpotential energy isleast orB, the speed at A and C is zero

66. A, because it is thehighest point oftravel

67. C, because thespring is stretchedthe maximumamount orC, because the KEand gravitationalPE are a minimum

68.

69. w = Fd sin w = (160. N)(10.m)(sin 30.°)w = 800 J

70. Credit forindicating kineticenergy when theblock is in position A and credit forindicating potentialenergy when theblock is in position B. Appropriateresponses include,but are not limitedto:Position A: kineticor KE, or energy ofmotionPosition B: elasticor potential, orenergy of position

71. PE = mg hPEs = kx2

kx2 = mg hk = 2mg h / x2

72. Credit for R, U, Y73. Credit for W, X, Z74. P = W/ t; P =

(680 N ×3.5m)/11.4s; P =208.8 J/s

Answer Key2015-16 Energy

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75. – The powerdeveloped duringthe 11.4 -secondtrial is less.– The powerdeveloped duringthe 11.4 -secondtrial is less than thepower developedduring the 8.5-second trial.

76. 24 m 1 m77. PE = 152,880

kg•m2/s2 or PE =1.5 × 105 J

78. The kinetic energyof the car at the topof the second hill isless than the kineticenergy of the car atthe top of the thirdhill. or The car's KE isless.

79. Acceptableresponses: PE = mg h; PE =(20. kg)(9.8 m/s2

)(5.0 m); PE =980 J; or PE = 9.8 × 102 kg•m2/s2

80. 980 J; Allow creditfor an answer thatis consistent withthe student’sanswer to theprevious question.

81.