Part II Review Unit Review NameWork Energy Power

Base your answers to questions 1 through 4 on the diagram below which shows a 20-newton forcepulling an object up a hill at a constant rate of 2 meters per second.

A) 0 kg-m/s B) 10 kg-m/s C) 100 kg-m/s D) 600 kg-m/s

1. The magnitude of the momentum of the moving object is

A) 100 J B) 200 J C) 500 J D) 600 J

2. The work done against gravity in moving the object from point A to point B is approximately

A) 5 J B) 10 J C) 15 J D) 50 J

3. The kinetic energy of the moving object is

A) 50 J B) 100 J C) 500 J D) 600 J

4. The work done by the force in pulling the object from A to B is

A) 120. J B) 422 JC) 570. J D) 992 J

5. A 15.0-kilogram mass is moving at 7.50 meters persecond on a horizontal, frictionless surface. What isthe total work that must be done on the mass toincrease its speed to 11.5 meters per second?

A) The kinetic energy increases and thegravitational potential energy remains the same.

B) The kinetic energy increases and thegravitational potential energy decreases.

C) The kinetic energy decreases and thegravitational potential energy remains thesame.

D) The kinetic energy decreases and thegravitational potential energy increases.

6. A shopping cart slows as it moves along a level floor.Which statement describes the energies of the cart?

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

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

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

Unit Review

8. Base your answer to the following question on the diagram below that shows an object at A that moves over a frictionless surface from A to E. Theobject has a mass of M.

A) A B) B C) D D) E

The object's kinetic energy at point C is less than its kinetic energy at point

A) B) C) D)

9. Two objects, A and B, are held one meter above thehorizontal ground. The mass of B is twice as great asthe mass of A. If PE is the gravitational potentialenergy of A relative to the ground, then thegravitational potential energy of B relative to theground is

A) Kinetic energy decreases and total mechanicalenergy increases.

B) Kinetic energy decreases and total mechanicalenergy remains the same.

C) Kinetic energy remains the same and totalmechanical energy increases.

D) Kinetic energy remains the same and totalmechanical energy remains the same.

10. Which statement describes the kinetic energy andtotal mechanical energy of a block as it is pulled atconstant speed up an incline?

A) increases and its kinetic energy decreasesB) increases and its kinetic energy remains the

sameC) remains the same and its kinetic energy

decreasesD) remains the same and its kinetic energy remains

the same

11. A car travels at constant speed v up a hill from point A to point B, as shown in the diagram below.

As the car travels from A to B, its gravitationalpotential energy

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

12. An object weighing 15 Newtons is lifted from theground to a height of 0.22 meter. The increase in theobject’s gravitational potential energy isapproximately

Unit Review

Base your answers to questions 13 through 16 on the diagram below which shows a 1-kilogram stonebeing dropped from rest from a bridge 100 meters above a gorge.

A) 98 J B) 490 J C) 50 J D) 100 J

13. What will be the kinetic energy of the stone after it has fallen 50 meters?

A) decreases B) increasesC) remains the same

14. As the stone falls, the gravitational potential energy of the stone

A) B)

C) D)

15. Which graph of distance traveled versus time represents the motion of the freely falling stone?

A) .98 N B) 9.8 NC) 98 N D) 980 N

16. What is the weight of the stone?

A) 1 joule B) 50 joulesC) 100 joules D) 0 joules

17. A cart weighing 10 Newtons is pushed 10 meters ona level surface by a force of 5 Newtons. What is theincrease in its potential energy?

A) 5.0 x 101 N/m B) 1.0 x 102 N/mC) 2.5 x 102 N/m D) 5.0 x 102 N/m

18. A spring stores 10 joules of elastic potential energywhen it is compressed 0.20 meter. What is the springconstant of the spring?

Unit Review

A) 14 m/s B) 6.0 m/sC) 3.0 m/s D) 2.6 m/s

19. A 7.0-kilogram cart, A, and a 3.0-kilogram cart, B,are initially held together at rest on a horizontal,frictionless surface. When a compressed springattached to one of the carts is released, the carts arepushed apart. After the spring is released, the speedof cart B is 6.0 meters per second, as represented inthe diagram below.

What is the speed of cart A after the spring isreleased?

A) 60.0 J B) 30.0 JC) 15.0 J D) 7.50 J

20. When a mass is placed on a spring with a springconstant of 60.0 newtons per meter, the spring iscompressed 0.500 meter. How much energy is storedin the spring?

A) 9.36 N/m B) 18.7 N/mC) 37.4 N/m D) 74.9 N/m

21. A spring gains 2.34 joules of elastic potential energyas it is compressed 0.250 meter from its equilibriumposition. What is the spring constant of this spring?

A) 32 N/m B) 16 N/mC) 8.0 N/m D) 4.0 N/m

22. The diagram below shows a toy cart possessing 16joules of kinetic energy traveling on a frictionless,horizontal surface toward a horizontal spring.

If the cart comes to rest after compressing the springa distance of 1.0 meter, what is the spring constantof the spring?

A) 0.41 m B) 41 mC) 410 m D) 4.1 m

23. The work done on a slingshot is 40.0 joules to pullback a 0.10-kilogram stone. If the slingshot projectsthe stone straight up in the air, what is the maximumheight to which the stone will rise? [Neglectfriction.]

A) 38 N/m B) 67 N/mC) 130 N/m D) 650 N/m

24. The diagram above represents a spring hangingvertically that stretches 0.075 meter when a 5.0-newton block is attached. The spring-block system isat rest in the position shown.

The value of the spring constant is

A) 3.6 J B) 7.2 J C) 12 J D) 24 J

25. A spring with a spring constant of 80. newtons permeter is displaced 0.30 meter from its equilibriumposition. The potential energy stored in the spring is

Unit Review

A) A B) B C) C D) D

26. The graph below represents the relationship betweenthe force applied to a spring and spring elongationfor four different springs.

Which spring has the greatest spring constant?

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

27. As shown in the diagram below, a 0.50-meter-longspring is stretched from its equilibrium position to alength of 1.00 meter by a weight.

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

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

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

A) smaller B) largerC) the same

29. The graph below shows elongation as a function ofthe applied force for two springs, A and B.

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

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

30. The graph below shows the relationship between theelongation of a spring and the force applied to thespring causing it to stretch.

What is the spring constant for this spring?

Unit Review

A) 4.8 J B) 6.0 J C) 9.8 J D) 24 J

31. The graph below represents the elongation of aspring as a function of the applied force.

How much work must be done to stretch the spring0.40 meter?

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

32. In the diagram below, a student compresses thespring in a pop-up toy 0.020 meter.

If the spring has a spring constant of 340 newtonsper meter, how much energy is being stored in thespring?

A) 1.0 N/m B) 2.5 N/mC) 0.20 N/m D) 0.40 N/m

33. The graph below represents the relationship betweenthe force applied to a spring and the compression(displacement) of the spring.

What is the spring constant for this spring?

A) 40 J B) 100 JC) 200 J D) 1000 J

34. A horizontal force of 20 newtons eastward causes a10-kilogram box to have a displacement of 5 meterseastward. The total work done on the box by the20-newton force is

A) 0.03 J B) 0.1 JC) 0.3 J D) 0.4 J

35. How much work is done by the force lifting a0.1-kilogram hamburger vertically upward atconstant velocity 0.3 meter from a table?

A) 150 J B) 250 JC) 450 J D) 750 J

36. As a box is pushed 30. meters across a horizontalfloor by a constant horizontal force of 25 newtons,the kinetic energy of the box increases by 300.joules. How much total internal energy is producedduring this process?

Unit Review

A) 0.15 J B) 1.5 JC) 15 J D) 150 J

37. The total work done in lifting a typical high schoolphysics textbook a vertical distance of 0.10 meter isapproximately

A) 1700 W B) 340 WC) 180 W D) 7.0 W

38. What is the rate at which work is done in lifting a35-kilogram object vertically at a constant speed of5.0 meters per second?

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

39. A student applies a 20.-newton force to move a crateat a constant speed of 4.0 meters per second across arough floor. How much work is done by the studenton the crate in 6.0 seconds?

A) 0.40 N B) 0.90 NC) 10. N D) 15 N

40. A 1.5-kilogram cart initially moves at 2.0 meters persecond. It is brought to rest by a constant net force in0.30 second. What is the magnitude of the net force?

A) 6 J B) 9 J C) 18 J D) 44 J

41. A 2.0-kilogram block sliding down a ramp from aheight of 3.0 meters above the ground reaches theground with a kinetic energy of 50. joules. The totalwork done by friction on the block as it slides downthe ramp is approximately

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

42. 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 3.00meters.

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

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

43. A block weighing 15 Newtons is pulled to the top ofan incline that is 0.20 meter above the ground, asshown below.

If 4.0 joules of work are needed to pull the block thefull length of the incline, how much work is doneagainst friction?

Unit Review

A) 40. J B) 360 JC) 400. J D) 760 J

44. In the diagram below, 400. joules of work is doneraising a 72-newton weight a vertical distance of 5.0meters.

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

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

45. The diagram below shows a 5.0-kilogram masssliding 9.0 meters down an incline from a height of2.0 meters in 3.0 seconds. The object gains 90.joules of kinetic energy while sliding.

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

A) 18 J B) 24 J C) 30. J D) 42 J

46. A student pulls a block 3.0 meters along a horizontalsurface at constant velocity. The diagram belowshows the components of the force exerted on theblock by the student.

How much work is done against friction?

A) 5 J B) 5.5 J C) 11 J D) 50. J

47. In the diagram below, 55 joules of work is needed toraise a 10.-newton weight 5.0 meters.

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

A) 0 J B) 50 J C) 250 J D) 300 J

48. A crate is pulled 6.0 meters up an incline with aforce of 50 Newtons. If the potential energy of thebox increases 250 joules, the total work done againstfriction in moving the box is

A) 100 J B) 200 JC) 300 J D) 400 J

49. A box is dragged up an incline a distance of 8 meterswith a force of 50 Newtons. If the increase inpotential energy of the box is 300 joules, the workdone against friction is

Unit Review

A) 8.0 W B) 40. WC) 96 W D) 2400 W

50. A motor does a total of 480 joules of work in 5.0seconds to lift a 12-kilogram block to the top of aramp. The average power developed by the motor is

A) 0.28 m/s B) 0.36 m/sC) 2.8 m/s D) 3.6 m/s

51. A 5.8 x 104-watt elevator motor can lift a totalweight of 2.1 x 104 newtons with a maximumconstant speed of

A) 490 N B) 30. NC) 3.0 N D) 0 N

52. A 70.-kilogram cyclist develops 210 watts of powerwhile pedaling at a constant velocity of 7.0 metersper second east. What average force is exertedeastward on the bicycle to maintain this constantspeed?

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

53. A 95-kilogram student climbs 4.0 meters up a ropein 3.0 seconds. What is the power output of thestudent?

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

54. A 3.0-kilogram block is initially at rest on africtionless, horizontal surface. The block is moved8.0 meters in 2.0 seconds by the application of a12-newton horizontal force, as shown in the diagrambelow.

What is the average power developed while movingthe block?

A) 3.0 J B) 15 J C) 20. J D) 75 J

55. A block initially at rest on a horizontal, frictionlesssurface is accelerated by a constant horizontal forceof 5.0 newtons. If 15 joules of work is done on theblock by this force while accelerating it, the kineticenergy of the block increases by

A) 28.4 J B) 279 JC) 868 J D) 2740 J

56. The diagram below represents a 155-newton box ona ramp. Applied force F causes the box to slide frompoint A to point B.

What is the total amount of gravitational potentialenergy gained by the box?

A) 6.0 J B) 15 J C) 30. J D) 90. J

57. A horizontal force of 5.0 newtons acts on a3.0-kilogram mass over a distance of 6.0 metersalong a horizontal, frictionless surface. What is thechange in kinetic energy of the mass during itsmovement over the 6.0-meter distance?

A) 20. m B) 2.0 mC) 0.20 m D) 0.020 m

58. A child does 0.20 joule of work to compress thespring in a pop-up toy. If the mass of the toy is 0.010kilogram, what is the maximum vertical height thatthe toy can reach after the spring is released?

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

59. The diagram below shows a 0.1-kilogram appleattached to a branch of a tree 2 meters above aspring on the ground below.

The apple falls and hits the spring, compressing it0.1 meter from its rest position. If all of thegravitational potential energy of the apple on the treeis transferred to the spring when it is compressed,what is the spring constant of this spring?

Unit Review

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

60. The spring of a toy car is wound by pushing the carbackward with an average force of 15 Newtonsthrough a distance of 0.50 meter. How much elasticpotential energy is stored in the car’s spring duringthis process?

A) 60. J B) 590 JC) 720 J D) 1,200 J

61. A 10.-kilogram mass falls freely a distance of 6.0meters near the Earth's surface. The total kineticenergy gained by the mass as it falls isapproximately

A) decreases by 5 J B) increases by 5 JC) decreases by 35 J D) increases by 35 J

62. A motor does 20. joules of work on a block,accelerating the block vertically upward. Neglectingfriction, if the gravitational potential energy of theblock increases by 15 joules, its kinetic energy

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

63. A 0.50-kilogram ball is thrown vertically upwardwith an initial kinetic energy of 25 joules.Approximately how high will the ball rise? [Neglectair resistance.]

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

64. The diagram below shows a moving, 5.00-kilogramcart at the foot of a hill 10.0 meters high. For the cartto reach the top of the hill, what is the minimumkinetic energy of the cart in the position shown?[Neglect energy loss due to friction.]

Unit Review

65. Base your answer to the following question on the diagram below. Which represents a 2.0-kilogram mass placed on a frictionless track at point A andreleased from rest. Assume the gravitational potential energy of the system to be zero at point E.

A) 10. m B) 20. m C) 30. m D) 40. m

As the mass travels along the track, the maximum height it will reach above point E will be closest to

A) Gravitational potential energy at ti is convertedto internal energy at tf.

B) Elastic potential energy at ti is converted tokinetic energy at tf.

C) Both elastic potential energy and kineticenergy at ti are converted to internal energyat tf.

D) Both kinetic energy and internal energy at ti areconverted to elastic potential energy at tf.

66. A wound spring provides the energy to propel a toycar across a level floor. At time ti,the car ismoving-at speed vi across the floor and the spring isunwinding, as shown below. At time tf, the springhas fully unwound and the car has coasted to a stop.

Which statement best describes the transformationof energy that occurs between the ti and tf?

67. Base your answer to the following question on thediagram below. The diagram represents a 1.00kilogram object being held at rest on a frictionlessincline.

A) 19.6 J B) 2.00 JC) 9.81 J D) 4.00 J

The object is released and slides the length of theincline. When it reaches the bottom of the incline,the object's kinetic energy will be closest to

A) 0.02 J B) 0.22 JC) 2.2 J D) 220 J

68. A 25-gram paper cup falls from rest off the edge of atabletop 0.90 meter above the floor. If the cup has0.20 joule of kinetic energy when it hits the floor,what is the total amount of energy converted intointernal (thermal) energy during the cup’s fall?

Unit Review

A) light energyB) nuclear energyC) gravitational potential energyD) internal energy

69. A car uses its brakes to stop on a level road. Duringthis process, there must be a conversion of kineticenergy into

Base your answers to questions 70 through 73 on the information and diagram below and on yourknowledge of physics.

As represented in the diagram a ski area rope-tow pulls a 72.0-kilogram skier from the bottomto the top of a 40.0-meter-high hill. The rope-tow exerts a force of magnitude 158 newtons tomove the skier a total distance of 230 meters up the side of the hill at constant speed.

70. Describe what happens to the total mechanical energy of the skier-hill system as the skier is pulled upthe hill.

71. Describe what happens to the internal energy of the skier-hill system as the skier is pulled up the hill.

72. Calculate the total amount of gravitational potential energy gained by the skier while moving up thehill. [Show all work, including the equation and the substitution with units]

73. Determine the total amount of work done by the rope on the skier.

74. Determine the amount of matter, in kilograms, that must be converted to energy to yield 1.0gigajoule.

Unit Review

75. The diagram below represents a 35-newton block hanging from a vertical spring, causing the springto elongate from its original length.

Determine the spring constant of the spring.

Base your answers to questions 76 through 78 on the information and diagram below and on yourknowledge of physics.

A jack-in-the-box is a toy in which a figure in an open box is pushed down, compressing aspring. The lid of the box is then closed. When the box is opened, the figure is pushed up by thespring. The spring in the toy is compressed 0.070 meter by using a downward force of 12.0newtons.

76. Identify one form of energy to which the elastic potential energy of the spring is converted when thefigure is pushed up by the spring.

77. Calculate the total amount of elastic potential energy stored in the spring when it is compressed.[Show all work, including the equation and substitution with units.]

78. Calculate the spring constant of the spring. [Show all work, including the equation and substitutionwith units.]

Unit Review

Base your answers to questions 79 and 80 on the information below and on your knowledge ofphysics.

An electron traveling with a speed of meters per second collides with a photon having afrequency of hertz. After the collision, the photon has joule of energy.

79. Determine the energy lost by the photon during the collision.

80. Calculate the original kinetic energy of the electron. [Show all work, including the equation andsubstitution with units.]

81. Regardless of the method used to generate electrical energy, the amount of energy provided by thesource is always greater than the amount of electrical energy produced. Explain why there is adifference between the amount of energy provided by the source and the amount of electrical energyproduced.

82. Calculate the average power required to lift a 490-newton object a vertical distance of 2.0 meters in10. seconds. [Show all work, including the equation and substitution with units.]

Base your answers to questions 83 and 84 on the information below.

A vertically hung spring has a spring constant of 150. newtons per meter. A2.00-kilogram mass is suspended from the spring and allowed to come to rest.

83. Calculate the total elastic potential energy stored in the spring due to the suspended 2.00-kilogrammass. [Show all work, including the equation and substitution with units.]

84. Calculate the elongation of the spring produced by the suspended 2.00-kilogram mass. [Show allwork, including the equation and substitution with units.]

85. When a spring is compressed 2.50 x 10–2 meter fromits equilibrium position, the total potentialenergy stored in the spring is 1.25 x 10–2 joule.Calculate the spring constant of the spring. [Show allwork, including the equation and substitution withunits.]

Base your answers to questions 86 through 88 on the information below.

A roller coaster car has a mass of 290. kilograms. Starting from rest, the car acquires 3.13 ×105 joules of kinetic energy as it descends to the bottom of a hill in 5.3 seconds.

86. Calculate the magnitude of the average acceleration of the roller coaster car as it descends to thebottom of the hill. [Show all work, including the equation and substitution with units.]

87. Calculate the speed of the roller coaster car at the bottom of the hill. [Show all work, including theequation and substitution with units.]

Unit Review

88. Calculate the height of the hill. [Neglect friction.] [Show all work, including the equation andsubstitution with units.]

89. A 10.-newton force compresses a spring 0.25 meterfrom its equilibrium position. Calculate the springconstant of this spring. [Show all work, includingthe equation and substitution with units.]

90. A box at the top of a rough incline possesses 981joules more gravitational potential energy than itdoes at the bottom. As the box slides to the bottomof the incline, 245 joules of heat is produced.Determine the kinetic energy of the box at thebottom of the incline.

91. A car, initially traveling at 30. meters per second,slows uniformly as it skids to a stop after the brakesare applied. On the axes below, sketch a graphshowing the relationship between the kinetic energyof the car as it is being brought to a stop and thework done by friction in stopping the car.

92. A spring in a toy car is compressed a distance, x. When released, the spring returns to its originallength, transferring its energy to the car.Consequently, the car having mass m moves withspeed v.

Derive the spring constant, k, of the car’s spring interms of m, x, and v. [Assume an ideal mechanicalsystem with no loss of energy.] [Show all work,including the equations used to derive the springconstant.

Unit Review

93. Base your answer to the following question on the information and diagram below.

A 10.-kilogram block is pushed across a floor by a horizontal force of 50. newtons. Theblock moves from point A to point B in 3.0 seconds.

Calculate the power required to move the block from point A to point B in 3.0 seconds. [Show allwork, including the equation and substitution with units.]

Base your answers to questions 94 through 96 on theinformation and diagram below.

A 1000.-kilogram empty cart moving with aspeed of 6.0 meters per second is about to collidewith a stationary loaded cart having a total massof 5000. kilograms, as shown. After the collision,the carts lock and move together. [Assumefriction is negligible.]

94. How does the kinetic energy of the combined cartsafter the collision compare to the kinetic energy ofthe carts before the collision?

95. Calculate the kinetic energy of the combined cartsafter the collision.

96. Calculate the speed of the combined carts after thecollision.

Base your answers to questions 97 through 99 on theinformation below.

The driver of a car made an emergency stopon a straight horizontal road. The wheels lockedand the car skidded to a stop. The marks made bythe rubber tires on the dry asphalt are 16 meterslong, and the car’s mass is 1200 kilograms.

97. Assuming that energy is conserved, calculate thespeed of the car before the brakes were applied.

98. Calculate the work done by the frictional force instopping the car.

99. Calculate the magnitude of the frictional force theroad applied to the car in stopping it.

Unit Review

Base your answers to questions 100 and 101 on theinformation below.

A 50.-kilogram child running at 6.0 meters persecond jumps onto a stationary 10.-kilogram sled.The sled is on a level frictionless surface.

100. After a short time, the moving sled with the childaboard reaches a rough level surface that exerts aconstant frictional force of 54 newtons on the sled.How much work must be done by friction to bringthe sled with the child to a stop?

101. a Calculate the speed of the sled with the child aftershe jumps onto the sled. [Show all work, includingthe equation and substitution with units.]b Calculate the kinetic energy of the sled with thechild after she jumps onto the sled.[Show all work,including the equation and substitution with units.]

Base your answers to questions 102 through 104 onthe information and diagram below.

A mass, M, is hung from a spring and reachesequilibrium at position B. The mass is then raisedto position A and released. The mass oscillatesbetween positions A and C. [Neglect friction.]

102. At which position, A, B, or C, is mass M locatedwhen the elastic potential energy of the system is ata maximum? Explain your choice.

103. At which position, A, B, or C, is mass M locatedwhen the gravitational potential energy of thesystem is at a maximum? Explain your choice.

104. At which position, A, B, or C, is mass M locatedwhen the kinetic energy of the system is at amaximum? Explain your choice.

Unit Review

105. Base your answer to the following question on the information below and on your knowledge ofphysics.

Using a spring toy like the one shown in the diagram, a physics teacher pushes on the toy,compressing the spring, causing the suction cup to stick to the base of the toy.

When the teacher removes her hand, the toy pops straight up and just brushes against the ceiling.She does this demonstration five times, always with the same result.

When the teacher repeats the demonstration for the sixth time the toy crashes against the ceilingwith considerable force. The students notice that in this trial, the spring and toy separated fromthe base at the moment the spring released.

The teacher puts the toy back together, repeats the demonstration and the toy once again justbrushes against the ceiling.

Explain, in terms of mass and energy, why the spring toy hits the ceiling in the sixth trial and not inthe other trials.

Base your answers to questions 106 through 108 on the information below.

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

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

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

108. Determine the work done by the 680-newton student in climbing the stairs.[Show all work including equation and substitution with appropriate units]

Unit Review

Base your answers to questions 109 through 111 on the information and diagram below.

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

109. On the axes provided above, sketch a graph of the gravitational potential energy of the block as afunction of its kinetic energy for the complete slide. Label your graph with appropriate values andunits.

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

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

112. The diagram below shows a spring compressed bya force of 6.0 Newtons from its rest position to itscompressed position.

Calculate the spring constant for this spring. [Showall calculations, including equations andsubstitutions with units.]

Answer KeyPart II) Energy Power Work

1. B2. C3. B4. D5. C6. C7. B8. B9. B10. C11. B12. C13. B14. A15. A16. B17. D18. D19. D20. D21. D22. A23. B24. B25. A26. A27. C28. B29. B30. D31. A32. A33. B34. B35. C36. C

37. B38. A39. D40. C41. B42. B43. A44. A45. B46. B47. A48. B49. A50. C51. C52. B53. C54. C55. B56. B57. C58. B59. D60. B61. B62. B63. B64. D65. D66. C67. A68. A69. D70. Total mechanical

energy increases.

71. Internal energyincreases.

72.

73. 3.63 x 104 J or36300 J

74. 1.1 x 10-8 kg75. 350 N/m76. — kinetic energy —

sound — internalenergy (thermalenergy) —gravitationalpotential energy(potential energy)

77. Equation andsubstitution withunits or for ananswer, with units,that is consistentwith the student'sresponse toquestions 71.

78. Equation andsubstitution withunits.

79.80.

81. — Energy is neededto overcome friction.— Energy isconverted intointernal (thermal)energy in themoving parts. —Energy is convertedinto sound.

82. P = 98 W83.

84.

85.

86.

87.

88.89.

90. 736 J

Answer KeyPart II) Energy Power Work

91.

92.

93. P = Fd

tP = (50. N)(8.0 m)

3.0 sP = 130 W or 133 W

94. The KE of thecombined carts afterthe collision is lessthan the KE of thecarts before thecollision.

95. KE = 3.0 x 103 J96. vf = 1.0 m/s97. v = 15 m/s or vi =

14.6 m/s98. W = 1.3 × 105 J or

128,000 J99. Ff = 8,000 N or

8,040 N100. 750 J

101. a Pbefore = Pafter or

mbeforevbefore = maftervafter

(50. kg)(6.0 m/s) =(60. kg) vafter

vafter = (50. kg) (6.0m/s) / (60. kg)

vafter = 5.0 m/s

b KE = mv2

KE = (60. kg)(5.0m/s)2

KE = 750 J102. C, because the

spring is stretchedthe maximumamount orC, because the KEand gravitational PEare a minimum

103. A, because it is thehighest point oftravel

104. B, because the masshas the greatestspeed orB, because the totalpotential energy isleast orB, the speed at A andC is zero

105. examples:– The toy has lessmass without thebase but the sameenergy. Therefore itcan go higher.– The work put intothe toy is the samebut the mass is less.With less mass thetoy could go higherbecause it is movingfaster.

106. – The powerdeveloped duringthe 11.4 -second trialis less.– The powerdeveloped duringthe 11.4 -second trialis less than thepower developedduring the 8.5-second trial.

107. P = W/ t; P = (680N × 3.5m)/11.4s; P= 208.8 J/s

108. W = F s; W = 680N × 3.5 m; W =2400 J

109.

110. 980 J; Allow creditfor an answer that isconsistent with thestudent’s answer tothe previousquestion.

111. 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

112. F = kx; 6.0 N =k(0.040 m ); k = 150N/m