Deck 4: Momentum and Energy

Question 1

A heavy truck and a small truck roll down a hill. Neglecting friction, at the bottom of the hill, the heavy truck will have greater

A)speed.
B)acceleration.
C)momentum.
D)all of the above
E)none of the above

Answer 1

C

Question 2

The conservation of momentum is most closely related to

A)Newton's First Law.
B)Newton's Second Law.
C)Newton's Third Law.

Answer 2

C

Question 3

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.

Answer 3

B

Question 4

Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has

A)increased time of impact.
B)decreased impulse.
C)decreased impact force.
D)both A and B
E)both A and C

Question 5

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 the above
E)none of the above

Question 6

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 the above

Question 7

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

Question 8

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)long time OR short time (same way either way).

Question 9

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 player's 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 the above

Question 10

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.

Question 11

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)48 m/s
E)none of the above

Question 12

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 the cannon is smaller.

Question 13

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 the above
E)none of the above

Question 14

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.

Question 15

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 ten times more than for a stiff-legged landing. In this way, the average force your body experiences is reduced by

A)less than ten times.
B)more than ten times.
C)about ten times.

Question 16

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.
D)all of the above
E)none of the above

Question 17

A moving object on which no forces are acting will continue to move with constant

A)acceleration.
B)impulse.
C)momentum.
D)all of the above
E)none of the above

Question 18

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 the above

Question 19

The impulse-momentum relationship is a direct result of

A)Newton's First Law.
B)Newton's Second Law.
C)Newton's Third Law.

Question 20

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.
C)both A and B
D)neither A nor B

Question 21

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.

Question 22

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 the above

Question 23

A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish at rest. The speed of the larger fish after lunch is

A)1/2 m/s.
B)2/5 m/s.
C)5/6 m/s.
D)6/5 m/s.
E)1 m/s.

Question 24

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 A and B
D)none of the above

Question 25

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)1/4 m/s.
B)1/5 m/s.
C)1/6 m/s.
D)none of the above
E)not enough information given

Question 26

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.

Question 27

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/s. The girl's speed is

A)0)45 m/s.
B)0)55 m/s.
C)0)83 m/s.
D)1)2 m/s.

Question 28

A piece of putty moving with 1 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 given

Question 29

A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 1/100 kg at a speed of 200 m/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 the above

Question 30

A karate expert executes a swift blow and severs a cement block in two 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 the above
E)none of the above

Question 31

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 at the same speed. It would be more damaging to hit the

A)car.
B)wall.
C)both the same

Question 32

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)0)5 m/s.
D)0)05 m/s.

Question 33

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.

Question 34

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 the above

Question 35

A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish swimming toward it at 4 m/s. The speed of the larger fish after lunch is

A)1/2 m/s.
B)1/5 m/s.
C)1/6 m/s.
D)2/3 m/s.
E)3/2 m/s.

Question 36

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

Question 37

A 5.0-kg blob of clay moving at 2.0 m/s 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 m/s.
C)2)5 m/s.
D)none of the above

Question 38

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

Question 39

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.

Question 40

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 A and B
D)neither A nor B

Question 41

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.

Question 42

A 5000-kg freight car runs into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/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 the above

Question 43

The average momentum of a 70-kg runner who covers 400 m 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.

Question 44

If you push for an hour against a stationary wall, no work is done

A)on the wall.
B)at all.
C)both A and B
D)none of the above

Question 45

If you push an object with twice the work input for twice the time, your power input is

A)twice as much.
B)four times as much.
C)the same amount as for half the work in half the time.

Question 46

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.

Question 47

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.

Question 48

If you exert 1 N for a distance of 1 m in 1 s, you will deliver a power of

A)1 W.
B)2 W.
C)1/3 W.
D)3 W.
E)none of the above

Question 49

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 the above

Question 50

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 A and B
D)none of the above

Question 51

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)1/4 m/s.
B)1/5 m/s.
C)1/6 m/s.
D)1 m/s.
E)none of the above

Question 52

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.

Question 53

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.

Question 54

Two identical gliders slide toward each other on an air track. One moves at 1 m/s and the other at 2 m/s. They collide and stick. The combined mass moves at

A)1/2 m/s.
B)1/3 m/s.
C)1/6 m/s.
D)3/4 m/s.
E)1)5 m/s.

Question 55

A sandbag is motionless in outer space. A second sandbag with three times the mass moving at 12 m/s collides with it. 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 the above

Question 56

A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/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.
D)1/6 m/s.
E)1)5 m/s.

Question 57

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 the above

Question 58

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 A nor B

Question 59

You're driving down the highway and a bug spatters on your windshield. Which undergoes the greater change in momentum?

A)the bug
B)your car
C)both the same

Question 60

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 the above

Question 61

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.

Question 62

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

Question 63

A 2-kg mass is held 4 m 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 the above

Question 64

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?

A)4 N
B)10 N
C)40 N
D)160 N
E)none of the above

Question 65

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 A nor B

Question 66

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.

Question 67

A hydraulic press, like a simple level, properly arranged is capable of multiplying energy input.

A)sometimes true
B)always false

Question 68

Which requires more work: lifting a 50-kg sack vertically 2 m or lifting a 25-kg sack vertically 4 m?

A)lifting the 50-kg sack
B)lifting the 25-kg sack
C)Both require the same amount of work.

Question 69

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.

Question 70

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)1 m
B)2 m
C)3 m
D)4 m
E)none of the above

Question 71

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.

Question 72

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.

Question 73

A clerk can lift containers a vertical distance of 1 m or can roll them up a 2-m-long 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.

Question 74

If you exert 100 J in 50 s, your power output is

A)1/4 W.
B)1/2 W.
C)2 W.
D)4 W.
E)more than 4 W.

Question 75

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.

Question 76

In raising a 5000-N piano with a pulley system, it is noted that for every 1 m 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

Question 77

An object that has kinetic energy must be

A)moving.
B)falling.
C)at an elevated position.
D)at rest.
E)none of the above

Question 78

An object that has potential energy may have this energy because of its

A)speed.
B)acceleration.
C)momentum.
D)location.
E)none of the above

Question 79

The power expended when a barbell is raised 2.0 m in 2 s is

A)1 W.
B)4 W.
C)8 W.
D)dependent on the mass of the barbell.

Question 80

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.