# 1. Physics Practice Questions - Momentum and Energy- 1-83

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Conceptual Physics 10th Edition by Paul G. Hewitt.

### a pickup truck speeding along a highway

1. Which of the following has the largest momentum relative to the earth?
a. a tightrope walker crossing Niagara Falls
b. a pickup truck speeding along a highway
c. a Mack truck parked in a parking lot
d. the Science building on campus
e. a dog running down the street

### doubled

2. A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has
twice as much mass, its momentum is
a. zero.
b. doubled.
d. unchanged.

### momentum

3. A moving object on which no forces are acting will continue to move with constant
a. acceleration.
b. impulse.
c. momentum.
d. all of these
e. none of these

### time the force acts

4. The difference between impulse and impact force involves the
a. distance the force acts.
b. time the force acts.
c. difference between acceleration and velocity.
d. mass and its effect on resisting a change in momentum.

### the change in momentum

5. It is correct to say that impulse is equal to
a. momentum.
b. the change in momentum.
c. the force multiplied by the distance the force acts.
0 all of these
e. none of these

### Newton's second law

6. The impulse-momentum relationship is a direct result of
a. Newton's first law.
b. Newton's second law.
c. Newton's third law.

### Newton's third law

7. The conservation of momentum is most closely related to
a. Newton's first law.
b. Newton's second law.
c. Newton's third law.

### cannon has more mass than the ball

8. A cannon recoils from firing a cannonball. The speed of the cannon's recoil is small because the
a. force against the cannon is smaller than against the ball.
b. momentum is mainly concentrated in the ball.
c. cannon has more mass than the ball.
d. momentum of tl1ecannon is smaller.

### the target would be safer than the shooter

9. Suppose a gun were made of a strong but very light material. Suppose also that the pellet is
more massive than the gun itself. For such a weapon
a. the target would be safer than the shooter.
b. recoil problems would be lessened.
c. conservation of energy would not hold.
d. conservation of momentum would not hold.
e. both conservation of energy and momentum would not hold.

### momentum

10. Two objects, A and B have the same size and shape, but A is twice as heavy as B. When they
are dropped simultaneously from a tower, they reach the ground at the same time, but A has greater
a. speed.
b. acceleration.
c. momentum.
d. all of these
e. none of these

### momentum

11. Neglecting friction, at the bottom of the hill, A heavy truck and a small truck roll down a hill. the heavy truck will have greater
a. speed.
b. acceleration.
c. momentum.
d. all of these
e. none of these

### time of impact is increased

12. In order to catch a ball, a baseball player extends the hand forward before impact with the ball
and then lets it ride backward in the direction of the ball's motion upon impact. doing this reduces the force of impact on the players hand principally because the
a. force of impact is reduced.
b. relative velocity is less.
c. time of impact is increased.
d. time of impact is decreased.
e. none of these

13. When you jump from an elevated position you usually bend your knees upon reaching the
ground. By doing this, the time of the impact is about 10 times more than for a stiff-legged
landing. In this way the average force your body experiences is reduced by
a. less than 10 times.
b. more than 10 times.

### long time

14. When you are in the way of a fast-moving object and can't get out of its way, you will suffer a
smaller force of impact if you decrease its momentum over a
a. long time.
b. short time.
c. same way either way.

### all of these

15. A car traveling along the highway needs a certain amount of force exerted on it to stop. More
stopping force may be required when the car has
a. more mass.
b. more momentum.
c. less stopping distance.
d. all of these
e. none of these

### if the mass of the bullet equals the mass of the gun

16. A bullet is fired from a gun. The speed of the bullet will be about the same as the speed of the
recoiling gun
a. because momentum is conserved.
b. because velocity is conserved.
c. because both velocity and momentum are conserved.
d. if the mass of the bullet equals the mass of the gun.
e. none of these

### a and c (increased time of impact and decreased impact force)

17. Padded dashboards in cars are safer in an accident than non-padded ones because an occupant
hitting the dash has
a. increased time of impact.
b. decreased impulse.
c. decreased impact force.
d. a. and b.
e. a. and c.

### all of these

18. The force on an apple hitting the ground depends upon
a. the speed of the apple just before it hits.
b. the time of impact with the ground.
c. whether or not the apple bounces.
d. all of these

### longer time to stop

19. Compared with falling on a wooden floor, a wine glass may not break when it falls to a
carpeted floor because of the
a. lesser impulse in stopping.
b. longer time to stop.
e both of these
d. neither of these

### 3 m/s

20. A 4-kg ball has a momentum of 12 kg.m/ s. What is the ball's speed?
a. 3 m/s
b. 4 m/s
c. 12 m/s
d. 48m/s
e. none of these

### 12 kg

21. A ball is moving at 4 m/ s and has a momentum of 48 kg.m/ s. What is the ball's mass?
a. 4 kg
b. 12 kg
c. 48 kg
d. 192 kg
e. none of these

### zero

22. Recoil is noticeable if we throw a heavy ball while standing on roller skates. If instead we go
through the motions of throwing the ball but hold onto it, our net recoil will be
a. zero.
b. the same as before.
c. small, but noticeable.

### greater

23. A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the
same amount of time compared to the force that stops the car, the force needed to stop the
truck is
a. greater.
b. smaller.
c. the same.

### not enough information given to say

24 . A 1-N apple falls to the ground. The apple hits the ground with an impact force of about
a. 1 N.
b. 2 N.
c. 4 N.
d. 9.8 N.
e. not enough information given to say.

### all of these

25. A karate expert executes a swift blow and severs a cement block with her bare hand. The
magnitude is the same for the
a. impulse on both the block and the expert's hand.
b. force on both the block and the expert's hand.
c. time of impact on both the block and the expert's hand.
d. all of these
e. none of these

### 1 unit

26. A piece of putty moving with I unit of momentum strikes and sticks to a heavy bowling ball
that is initially at rest. After the putty sticks to the ball, both move with a combined momentum
of
a. less than 1 unit.
b. more than 1 unit.
c. 1 unit.
d. not enough information

### 1 kg·m/s

27. A 1-kg chunk of putty moving at 1 m/ s collides and sticks to a 5-kg bowling ball initially at
rest. The bowling ball and putty then move with a momentum of
a. 0 kg·m/s.
b. 1 kg·m/s.
c. 2 kg·m/s.
d. 5 kg·m/s.
e. more than 5 kg∙m/s.

### exhaust gases

28. The force that accelerates a rocket in outer space is exerted on the rocket by the
a. rocket's engine.
b. rocket's wings.
c. atmospheric pressure.
d. exhaust gases.
e. none of these

### 0 kg∙m/s

29. Two billiard balls having the same mass roll toward each other, each moving at the same
speed. What is the combined momentum of the two balls?
a. 0 kg∙m/s
b. 10 kg∙m/s

### depends on the time involved

30. Compared with the force that brings a small car to a stop, the force required to bring a heavy
truck traveling at the same speed to a stop
a. is less.
b. is more.
c. depends on the time involved.

### impulse

31. A cannonball shot from a cannon with a long barrel will have a greater muzzle velocity
because the cannonball receives a greater
a. force.
b. impulse.
c. both of these
d. neither of these

### jumper

32. According to the impulse-momentum equation Ft =change in (mv, a bungee jumper in fall
has momentum which is reduced by the force F exerted by the bungee cord. If m is the mass of
the jumper, then v in the equation is the speed of the
a. jumper.
b. cord.
c. both of these
d. none of these

### both the same

33. Consider driving into a massive concrete wall with no "give," versus having a head-on
collision at the same speed with an identical car moving toward you with the same speed. It
would be more damaging to hit the
a. car.
b. wall.
c. both the same

### 1 m/s

34. A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 1/100 kg at a speed
of 200m/s. The recoil velocity of the rifle is about
a. 0.001 m/s.
b. 0.01 m/s.
c. 0.1 m/s.
d 1 m/s.
e. none of these

### 5/6 m/s

35. A 5-kg fish swimming at a speed of 1 m/ s swallows an absent-minded I-kg fish at rest. The
speed of the larger fish after lunch is
a. 1/2m/s.
b. 2/5 m/s.
c. 5/6 m/s.
d. 6/5 m/s.
e. 1 m/s.

### 1/6 m/s

36. A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded I-kg fish swimming
toward it at 4 m/s. The speed of the larger fish after lunch is
a. 1/2 m/s.
b. 1/5m/s.
c. 1/6 m/s.
d. 2/3 m/s.
e. 3/2 m/s.

### 1/6 m/s

37. A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball that is
initially at rest. The bowling ball and putty are then set in motion with a speed of
a. ¼ m/s.
b. liS m/s.
c. 1/6 m/s.
d. none of these
e. not enough information given

### 1.1 m/s

38. A 5.0-kg blob of clay moving at 2.0mIs slams into a 4.0-kg blob of clay at rest. The speed of
the two blobs stuck together after colliding is about
a. 1.1 m/s.
b. 1.5 ml s.
c. 2.5 m/s.
d. none of these

### 0.83 m/s

39. A 30-kg girl and a 25-kg boy face each other on friction-free roller blades. The girl pushes the
boy, who moves away at a speed of 1.0 m Is. The girl's speed is
a. 0.45 m/s.
b. 0.55m/s.
c. 0.83 m/s.
d. 1.2 m/s.

### 0.05 m/s

40. If an astronaut whose total mass is 100 kg ejects 0.1 kg of gas at a speed of 50 m/s from her
propulsion pistol, her recoil speed is
a. 50 m/s.
b. 5.0 m/s.
c. O.5m/s.
d. 0.05 m/s.

### greater than that of the apple only if the apple bounces

41 Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by
the ground is
a. negligible compared to the momentum of the apple.
b. greater than that of the apple only if the apple bounces.
c. greater than that of the apple in all cases.
d. none of these

### both the same

42. You're driving down the highway and a bug spatters into your windshield. Which undergoes
the greater change in momentum?
a. the bug
c. both the same

### astronaut will never catch the first bounce

43. Suppose an astronaut in outer space wishes to play a solitary "throw, bounce, and catch" game
by tossing a ball against a very massive and perfectly elastic concrete wall. If the ball is as
massive as the astronaut, the
a. astronaut will catch one bounce only.
b. astronaut will never catch the first bounce.
c. astronaut's time between catches will decrease as the game progresses.
d. none of these

### 1/6 m/s

44. Consider massive gliders that slide friction-free along a horizontal air track. Glider a. has a
mass of 1 kg, a speed of 1 m/s, and collides with glider B, which has a mass of 5 kg and is at
rest. If they stick upon collision, their speed after collision will be
a. ¼ m/s.
b. 1/5 m/s.
c. 1/6 m/s.
d. 1 m/s.
e. none of these

### 1/3 m/s

45. A 1-kg glider and a 2-kg glider both slide toward each other at 1 ml s on an air track. They
collide and stick. The combined mass moves at
a. 0 m/s.
b. 1/2 m/s.
c. 1/3 m/s.
0 1/6 m/s.
e. 1.5 m/s.

### 1/2 m/s

46. Two identical gliders slide toward each other on an air track. One moves at 1 ml s and the
other at 2 m/s. They collide and stick. The combined mass moves at
a. 1/2 m/s.
b. 1/3m/s.
c. 1/6 m/s.
d. 3/4m/s.
e. 1.5 m/s.

### 6 m/s

47. A 5000-kg freight car runs into a 10,OOO-kgfreight car at rest. They couple upon collision and
move with a speed of 2m I s. What was the initial speed of the 5000-kg car?
a. 4 m/s
b. 5 m/s
c. 6 m/s
d. 8 m/s
e. none of these

### none of these

48. A sandbag is motionless in outer space. a. second sandbag with 3 times the mass moving at 12 m/s
collides with it and they both stick together, and move at a speed of
a. 3 m/s.
b. 4 m/s.
c. 6 m/s.
d. 8 m/s.
e. none of these

### 2000 N

49. A 1000-kg car moving at 10 m/s brakes to a stop in 5 s. The average braking force is
a. 1000 N.
b. 2000 N.
c. 3000 N.
d. 4000 N.
e. 5000 N.

### 1.5g

50. A bungee jumper attains a speed of 30 m/s just as the bungee cord begins to stretch. If the period of stretch is 2 s, the magnitude of the jumper's average deceleration is about
a. 0.5g.
b. g.
c. 1.5g.
d. 2g.
e. none of these

### velocity is minimum

51. A bungee jumper makes her jump. The force of the bungee cord on her is greatest when her
a. velocity is maximum.
b. velocity is minimum.
c. neither

### momentum

52. The average force that a bungee cord exerts on a jumper, multiplied by the time of stretch, equals the jumper's change in
a. velocity.
b. acceleration.
c. momentum.
d. kinetic energy.
e. all of these

### 560 kg∙m/s

53. The average momentum of a 70-kg runner who covers 400m in 50 s is
a. 8.75 kg∙m/s.
b. 57 kg∙m/s.
c. 560 kg∙m/s.
d. 5490 kg∙m/s.

### 8.0 N

54. A boxer punches a sheet of paper in midair and brings it from rest up to a speed of 40 m/s in 0.05 s. If the mass of the paper is 0.01 kg, the force of impact on the paper is about
a. 0.08 N.
b. 0.8 N.
c. 8.0 N.
d. 80 N.

### on the wall

55. If you push for an hour against a stationary wall, you do no work
a. on the wall.
b. at all.
c. both of these
d. none of these

### twice as much work

56. If you push an object twice as far while applying the same force, you do
a. twice as much work.
b. four times as much work.
c. the same amount of work.

### twice as much work

57. If you push an object just as far while applying twice the force, you do
a. twice as much work.
b. four times as much work.
c. the same amount of work.

### the same amount as for half the work in half the time

58. If you push an object with twice the work input for twice the time, your power input is
a. twice.
b. four times as much.
c. the same amount as for half the work in half the time.

### power

59. A job is done slowly, while an identical job is done quickly. Both jobs require the same amount
of work, but different amounts of
a. energy.
b. power.
c. both of these
d. none of these

### twice the usual power output

60. If you do work on an object in half the time, your power output is
a. half the usual power output.
b. the same power output.
c. twice the usual power output.

### 1 W

61. Exert 1 N for a distance of 1m in 1 s and you deliver a power of
a. 1 W.
b. 2 W.
c. 1/3 W.
d. 3 W.
e. none of these

### 2W

62. Exert 100 J in 50 s and your power output is
a. 1/4 W.
b. 1/2 W.
c. 2W.
d. 4W.
e. more than 4 W.

### twice as much potential energy

63. An object is raised above the ground gaining a certain amount of potential energy.
If the same object is raised twice as high, it gains
a. four times as much potential energy.
b. twice as much potential energy.
c. neither of these

### twice as much

64. When an object is lifted 10 m, it gains a certain amount of potential energy. If the same object is
lifted 20 m, its potential energy gain is
a. less.
b. the same.
c. twice as much.
d. four times as much.
e. more than four times as much.

### twice as much work

65. A 1000-kg car and a 2000-kg car are hoisted the same distance in a gas station. Raising the
more massive car requires
a. less work.
b. as much work.
c. twice as much work.
d. four times as much work.
e. more than four times as much work.

### moving

66. An object that has kinetic energy must be
a. moving.
b. falling.
c. at an elevated position.
d. at rest.
e. none of these

### location

67. An object that has potential energy may have this energy because of its
a. speed.
b. acceleration.
c. momentum.
d. location.
e. none of these

### decreased

68. Bullets are fired from an airplane in the forward direction of motion. The momentum of the
airplane will be
a. decreased.
b. unchanged.
c. increased.

### half as much

69. A clerk can lift containers a vertical distance of 1 m or can roll them up a 2-m-Iong ramp to the
same elevation. With the ramp, the applied force required is about
a. half as much.
b. twice as much.
c. the same.

### 40 J

70. A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a
kinetic energy of
a. less than 40 J.
b. more than 40 J
c. 40 J.

### heat

71. When a car is braked to a stop, its kinetic energy is transformed to
a. stopping energy.
b. potential energy.
c. energy of motion.
d. energy of rest.
e. heat.

### always false

72. A hydraulic press, like a simple level, properly arranged is capable of multiplying energy
input.
a. sometimes true
b. always false

### the force on the ball is at right angles to the ball's motion

73. No work is done by gravity on a bowling ball that rolls along a bowling alley because
a. no force acts on the ball.
b. no distance is covered by the ball.
c. the force on the ball is at right angles to the ball's motion.
d. no potential energy is being converted to kinetic energy.
e. its kinetic energy remains constant.

### Both require the same amount of work

74. Which requires more work: lifting a 50-kg sack vertically 2m or lifting a 25-kg sack vertically
4m?
a. lifting the 50-kg sack
b. lifting the 25-kg sack
c. Both require the same amount of work.

### the same

75. A 50-kg sack is lifted 2 m in the same time as a 25-kg sack is lifted 4 m. The power expended
in raising the 50-kg sack compared to the power used to lift the 25-kg sack is
a. twice as much.
b. half as much.
c. the same.

### 500 N

76. In raising a 5000 N piano with a pulley system, it is noted that for every 1m of rope pulled
down, the piano rises 0.1 m. Ideally, this means the force needed to lift it is about
a. 50 N.
b. 500 N.
c. 5000 N.
d. not enough information given to estimate

### dependent on the mass of the barbell

77. The power expended with a barbell is raised 2.0m in 2 s is
a. 1 W.
B. 4 W.
c. 8W.
d. dependent on the mass of the barbell

### 40 J

78. A. TV set is pushed a distance of 2 m with a force of 20 N that is in the same direction as the set moves. How much work is done on the set?
a. 2 J
b. 10 J
c. 20 J
d. 40 J
e. 80 J

### 10 N

79 It takes 40 J to push a large box 4 m across a floor. Assuming the push is in the same direction
as the move, what is the magnitude of the force on the box?
A4N
b. 10 N
c. 40 N
d. 160N
e. none of these

### 80 J

80. A 2-kg mass is held 4m above the ground. What is the approximate potential energy of the
mass with respect to the ground?
a. 20 J
b. 40 J
c. 60 J
d. 80 J
e. none of these

### 2m

81. A 2-kg mass has 40 J of potential energy with respect to the ground. Approximately how far is
it located above the ground?
a. 1m
b. 2m
c. 3m
d. 4m
e. none of these

### all of these

82. A heavy pile driver starting from rest falls on a pile with a force that depends on the
a. original height of the driver.
b. original potential energy of the driver.
c. distance the pile falls.
d. all of these
e. none of these

### 50W

83. Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 s.
How much power does the elevator use?
a. 20W
b. 50W
c. 100W
d. 1000W
e. 20,000W

Example: