1. Physics Practice Questions - Momentum and Energy- 1-83
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
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
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
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.
The baseball is hit straight back to the pitcher at a speed of 110 km/h.
A baseball is pitched horizontally toward home plate with a velocity of 110 km/h. In which of the following scenarios does the baseball have the largest change in momentum?
The law of conservation of momentum states that the total momentum in an isolated system of objects must remain constant, regardless of the interactions (or collisions) between the objects. Thus, the total momentum of the two pieces of the egg after the explosion must be equal to the total momentum of the two pieces of the egg before the explosion
Conservation of Momentum
constant
The law of conservation of momentum is the total momentum of an isolated system remains ____.
elastic collsion
What do you call a collision where the total Kinetic energy is conserved? (momentum is conserved)
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
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
decreases
A small boat coasts at constant speed under a bridge. A heavy sack of sand is dropped from the bridge onto the boat. The speed of the boat
Throw it directly away from the space station
An astronaut is a short distance away from her space station without a tether rope. She has a large wrench. What should she do with the wrench to move toward the space station?
momentum after
As long as there are no external forces, momentum before=
inelastic
One in which the total kinetic energy of the system after the collision is not equal to the total kinetic energy before the collision, if the objects stick together after colliding, the collision is said to be completely _______. (momentum is conserved)
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.
TOTAL
Remember that while kinetic energy isn't always conserved, ______ energy is always conserved.
the super ball
You are lying in bed and want to shut your bedroom door. You have a bouncy "superball" and a blob of clay, both with the same mass. which have the largest change in momentum?
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
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
about 10 times
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. c. about 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.
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
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. c. quadrupled. d. unchanged.
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 c. more information needed to determine
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
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.
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.
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 b. your car 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.
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
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
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
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.
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
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
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.
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.
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
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.
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
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.
The golf ball
A golf ball and an equal-mass bean bag are dropped from the same height and hit the ground. The bean bag stays on the ground while the golf ball rebounds. Which experiences the greater impulse from the ground? The golf ball. The bean bag. Both the same. Not enough information
They have the same momentum, but the car has more kinetic energy than the truck
A small car and a heavy pickup truck are both out of gas. The truck has twice the mass of the car. After you push both the car and the truck for the same amount of time with the same force, what can you say about the momentum and kinetic energy (KE) of the car and the truck? Ignore friction.
They have the same kinetic energy, but the truck has more momentum than the car.
A small car and a heavy pickup truck are both out of gas. The truck has twice the mass of the car. After you push both the car and the truck for the same distance with the same force, what can you say about the momentum and kinetic energy (KE) of the car and the truck? Ignore friction.
They both have the same change in magnitude of momentum because momentum is conserved.
A truck going 15 km/h has a head-on collision with a small car going 30 km/h. what is change in magnitude of momentum
only momentum is conserved
The space shuttle, in circular orbit around the Earth, collides with a small asteroid which ends up in the shuttle's storage bay. For this collision,
no difference
Two identical billiard balls traveling at the same speed have a head-on collision and rebound. If the balls had twice the mass, but maintained the same size and speed, how would the rebound be different?
Work W= Fdcos(theta)
____ is done on an object by a force when the object moves through a distance d.
