## University Physics with Modern Physics 14th Edition By Young – Test Bank

Exam

Name___________________________________

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1) Consider two less-than-desirable options. In the first you are driving 30 mph and crash

head-on into an identical car also going 30 mph. In the second option you are driving

30 mph and crash head-on into a stationary brick wall. In neither case does your car

bounce off the thing it hits, and the collision time is the same in both cases. Which of

these two situations would result in the greatest impact force?

A) hitting the other car

B) hitting the brick wall

C) The force would be the same in both cases.

D) We cannot answer this question without more information.

E) None of these is true.

1)

Answer: C

2) As a tile falls from the roof of a building to the ground its momentum is conserved.

A) True B) False

2)

Answer: B

3) You are standing on a skateboard, initially at rest. A friend throws a very heavy ball

towards you. You can either catch the object or deflect the object back towards your

friend (such that it moves away from you with the same speed as it was originally

thrown). What should you do in order to MINIMIZE your speed on the skateboard?

A) Deflect the ball.

B) Catch the ball.

C) Your final speed on the skateboard will be the same regardless whether you catch

the ball or deflect the ball.

3)

Answer: B

4) On a smooth horizontal floor, an object slides into a spring which is attached to another

mass that is initially stationary. When the spring is most compressed, both objects are

moving at the same speed. Ignoring friction, what is conserved during this interaction?

A) momentum only

B) momentum and potential energy

C) momentum and kinetic energy

D) kinetic energy only

E) momentum and mechanical energy

4)

Answer: E

1

5) A baseball is thrown vertically upward and feels no air resistance. As it is rising

A) both its momentum and its mechanical energy are conserved.

B) both its momentum and its kinetic energy are conserved.

C) its momentum is not conserved, but its mechanical energy is conserved.

D) its gravitational potential energy is not conserved, buts its momentum is

conserved.

E) its kinetic energy is conserved, but its momentum is not conserved.

5)

Answer: C

6) A small glider is coasting horizontally when suddenly a very heavy piece of cargo falls

out of the bottom of the plane. You can neglect air resistance. Just after the cargo has

fallen out

A) the plane speeds up and the cargo slows down.

B) neither the cargo nor the plane change speed.

C) the cargo slows down but the plane does not change speed.

D) the plane speeds up but the cargo does not change speed.

E) both the cargo and the plane speed up.

6)

Answer: B

7) A small car has a head-on collision with a large truck. Which of the following

statements concerning the magnitude of the average force due to the collision is

correct?

A) The small car and the truck experience the same average force.

B) The small car experiences the greater average force.

C) The truck experiences the greater average force.

D) It is impossible to tell since the masses are not given.

E) It is impossible to tell since the velocities are not given.

7)

Answer: A

8) In a collision between two objects having unequal masses, how does magnitude of the

impulse imparted to the lighter object by the heavier one compare with the magnitude

of the impulse imparted to the heavier object by the lighter one?

A) The heavier object receives a larger impulse.

B) The lighter object receives a larger impulse.

C) Both objects receive the same impulse.

D) The answer depends on the ratio of the masses.

E) The answer depends on the ratio of the speeds.

8)

Answer: C

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9) In a perfectly ELASTIC collision between two perfectly rigid objects

A) the momentum of each object is conserved.

B) the momentum of the system is conserved but the kinetic energy of the system is

not conserved.

C) both the momentum and the kinetic energy of the system are conserved.

D) the kinetic energy of the system is conserved, but the momentum of the system is

not conserved.

E) the kinetic energy of each object is conserved.

9)

Answer: C

10) In an INELASTIC collision between two objects

A) the momentum of each object is conserved.

B) the kinetic energy of each object is conserved.

C) the kinetic energy of the system is conserved, but the momentum of the system is

not conserved.

D) the momentum of the system is conserved but the kinetic energy of the system is

not conserved.

E) both the momentum and the kinetic energy of the system are conserved.

10)

Answer: D

11) A shell explodes into two fragments, one fragment 25 times heavier than the other. If

any gas from the explosion has negligible mass, then

A) the momentum change of the lighter fragment is exactly the same as the

momentum change of the heavier fragment.

B) the momentum change of the lighter fragment is 25 times as great as the

momentum change of the heavier fragment.

C) the kinetic energy change of the heavier fragment is 25 times as great as the

kinetic energy change of the lighter fragment.

D) the momentum change of the heavier fragment is 25 times as great as the

momentum change of the lighter fragment.

E) the kinetic energy change of the lighter fragment is 25 times as great as the kinetic

energy change of the heavier fragment.

11)

Answer: A

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12) Jacques and George meet in the middle of a lake while paddling in their canoes. They

come to a complete stop and talk for a while. When they are ready to leave, Jacques

pushes George’s canoe with a force F to separate the two canoes. What is correct to

say about the final momentum and kinetic energy of the system if we can neglect any

resistance due to the water?

A) The final momentum is in the direction of F but the final kinetic energy is zero.

B) The final momentum is in the direction of F and the final kinetic energy is

positive.

C) The final momentum is zero but the final kinetic energy is positive.

D) The final momentum is zero and the final kinetic energy is zero.

E) The final momentum is in the direction opposite of F but the final kinetic energy

is zero.

12)

Answer: E

13) A 1.0-kg block and a 2.0-kg block are pressed together on a horizontal frictionless

surface with a compressed very light spring between them. They are not attached to the

spring. After they are released and have both moved free of the spring

A) both blocks will both have the same amount of kinetic energy.

B) the heavier block will have more kinetic energy than the lighter block.

C) both blocks will have equal speeds.

D) the lighter block will have more kinetic energy than the heavier block.

E) the magnitude of the momentum of the heavier block will be greater than the

magnitude of the momentum of the lighter block.

13)

Answer: D

14) There must be equal amounts of mass on both side of the center of mass of an object.

A) True B) False

14)

Answer: B

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.

15) A time-varying horizontal force F(t) = At4 + Bt2 acts for 0.500 s on a 12.25-kg

object, starting at time t = 1.00 s. In the SI system, A has the numerical value

4.50 and B has the numerical value 8.75.

(a) What are the SI units of A and B?

(b) What impulse does this force impart to the object?

15)

Answer: (a) A: N/s4 = kg • m/s6, B: N/s2 = kg • m/s4 (b) 12.9 N • s,

horizontally

16) A 2.50-kg stone is dropped from rest at a height of 3.75 m. What impulse does

gravity impart to this stone from the instant it is dropped until it hits the ground,

assuming negligible air resistance?

16)

Answer: 21.4 N • s

4

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

17) A firecracker breaks up into several pieces, one of which has a mass of 200 g and flies

off along the x-axis with a speed of 82.0 m/s. A second piece has a mass of 300 g and

flies off along the y-axis with a speed of 45.0 m/s. What are the magnitude and

direction of the total momentum of these two pieces?

A) 21.2 kg • m/s at 39.5° from the x-axis

B) 21.2 kg • m/s at 56.3° from the x-axis

C) 361 kg • m/s at 0.983° from the x-axis

D) 361 kg • m/s at 56.3° from the x-axis

E) 93.5 kg • m/s at 28.8° from the x-axis

17)

Answer: A

18) A stationary 1.67-kg object is struck by a stick. The object experiences a horizontal

force given by F = at – bt2, where t is the time in milliseconds from the instant the stick

first contacts the object. If a = 1500 N/(ms) and b = 20 N/(ms)2, what is the speed of

the object just after it comes away from the stick at t = 2.74 ms?

A) 25 m/s B) 3.3 m/s C) 22 m/s D) 3.7 m/s

18)

Answer: B

19) During a collision with a wall, the velocity of a 0.200-kg ball changes from 20.0 m/s

toward the wall to 12.0 m/s away from the wall. If the time the ball was in contact with

the wall was 60.0 ms, what was the magnitude of the average force applied to the ball?

A) 16.7 N B) 107 N C) 13.3 N D) 40.0 N E) 26.7 N

19)

Answer: B

20) A 0.500-kg ball traveling horizontally on a frictionless surface approaches a very

massive stone at 20.0 m/s perpendicular to wall and rebounds with 70.0% of its initial

kinetic energy. What is the magnitude of the change in momentum of the stone?

A) 1.63 kg·m/s

B) 0.000 kg·m/s

C) 3.00 kg·m/s

D) 18.4 kg·m/s

E) 14.0 kg·m/s

20)

Answer: D

21) A 620-g object traveling at 2.1 m/s collides head-on with a 320-g object traveling in

the opposite direction at 3.8 m/s. If the collision is perfectly elastic, what is the change

in the kinetic energy of the 620-g object?

A) It loses 0.47 J.

B) It gains 0.69 J.

C) It loses 0.23 J.

D) It loses 1.4 J.

E) It doesn’t lose any kinetic energy because the collision is elastic.

21)

Answer: C

5

22) A 2.3-kg object traveling at 6.1 m/s collides head-on with a 3.5-kg object traveling in

the opposite direction at 4.8 m/s. If the collision is perfectly elastic, what is the final

speed of the 2.3-kg object?

A) 7.1 m/s B) 0.48

m/s

C) 3.8 m/s D) 4.3 m/s E) 6.6 m/s

22)

Answer: A

23) A car of mass 1689 kg collides head-on with a parked truck of mass 2000 kg. Spring

mounted bumpers ensure that the collision is essentially elastic. If the velocity of the

truck is 17 km/h (in the same direction as the car’s initial velocity) after the collision,

what was the initial speed of the car?

A) 19 km/h B) 38 km/h C) 10 km/h D) 29 km/h

23)

Answer: A

24) A block of mass m = 8.40 kg, moving on a horizontal frictionless surface with a speed

4.20 m/s, makes a perfectly elastic collision with a block of mass M at rest. After the

collision, the 8.40 block recoils with a speed of 0.400 m/s. In the figure, the blocks are

in contact for 0.200 s. The magnitude of the average force on the 8.40-kg block, while

the two blocks are in contact, is closest to

A) 193 N. B) 185 N. C) 168 N. D) 160 N. E) 176 N.

24)

Answer: A

25) A billiard ball traveling at 3.00 m/s collides perfectly elastically with an identical

billiard ball initially at rest on the level table. The initially moving billiard ball deflects

30.0° from its original direction. What is the speed of the initially stationary billiard

ball after the collision?

A) 2.59 m/s

B) 0.866 m/s

C) 0.750 m/s

D) 2.00 m/s

E) 1.50 m/s

25)

Answer: E

6

26) A pool player is attempting a fancy shot. He hits the cue ball giving it a speed of 5.57

m/s and directs its center on a path tangent to the surface of the target ball having the

same mass as the cue ball. After the collision (on a frictionless table) the

initially-stationary ball moves with a speed of 4.82 m/s. After the collision, the new

speed of the cue ball and the relative direction of the balls are closest to

A) 2.79 m/s, at 60° to each other. B) 8.34 m/s, at 60° to each other.

C) 8.34 m/s, at 90° to each other. D) 2.79 m/s, at 90° to each other.

26)

Answer: D

27) A 480-kg car moving at 14.4 m/s hits from behind a 570-kg car moving at 13.3 m/s in

the same direction. If the new speed of the heavier car is 14.0 m/s, what is the speed of

the lighter car after the collision, assuming that any unbalanced forces on the system

are negligibly small?

A) 10.5 m/s B) 5.24 m/s C) 13.6 m/s D) 19.9 m/s

27)

Answer: C

28) A 2.00-kg object traveling east at 20.0 m/s collides with a 3.00-kg object traveling west

at 10.0 m/s. After the collision, the 2.00-kg object has a velocity 5.00 m/s to the west.

How much kinetic energy was lost during the collision?

A) 175 J B) 516 J C) 0.000 J D) 91.7 J E) 458 J

28)

Answer: E

29) A 15-g bullet is shot vertically into an 2-kg block. The block lifts upward 8.0 mm (see

the figure). The bullet penetrates the block and comes to rest in it in a time interval of

0.0010 s. Assume the force on the bullet is constant during penetration and that air

resistance is negligible. The initial kinetic energy of the bullet is closest to

A) 10 J. B) 0.0012

J.

C) 21 J. D) 14 J. E) 0.16 J.

29)

Answer: C

7

30) Two objects of the same mass move along the same line in opposite directions. The

first mass is moving with speed v. The objects collide, stick together, and move with

speed 0.100v in the direction of the velocity of the first mass before the collision. What

was the speed of the second mass before the collision?

A) 0.900v B) 0.800v C) 10.0v D) 1.20v E) 0.00v

30)

Answer: B

31) An 8.0-g bullet is shot into a 4.0-kg block, at rest on a frictionless horizontal surface

(see the figure). The bullet remains lodged in the block. The block moves into an ideal

massless spring and compresses it by 8.7 cm. The spring constant of the spring is 2400

N/m. The initial velocity of the bullet is closest to

A) 1000 m/s.

B) 1300 m/s.

C) 900 m/s.

D) 1100 m/s.

E) 1200 m/s.

31)

Answer: D

32) In the figure, determine the character of the collision. The masses of the blocks, and the

velocities before and after are given. The collision is

A) perfectly elastic.

B) completely inelastic.

C) partially inelastic.

D) characterized by an increase in kinetic energy.

E) not possible because momentum is not conserved.

32)

Answer: A

8

33) In the figure, determine the character of the collision. The masses of the blocks, and the

velocities before and after are given, and no other unbalanced forces act on these

blocks. The collision is

A) completely inelastic.

B) partially inelastic.

C) perfectly elastic.

D) characterized by an increase in kinetic energy.

E) not possible because momentum is not conserved.

33)

Answer: E

34) A 5.00-kg ball is hanging from a long but very light flexible wire when it is struck by a

1.50-kg stone traveling horizontally to the right at 12.0 m/s. The stone rebounds to the

left with a speed of 8.50 m/s, and the ball swings to a maximum height h above its

original level. The value of h is closest to

A) 1.93 m.

B) 1.10 m.

C) 0.0563 m.

D) 3.69 m.

E) 2.20 m.

34)

Answer: A

35) A 1000-kg car approaches an intersection traveling north at 20.0 m/s. A 1200-kg car

approaches the same intersection traveling east at 22.0 m/s. The two cars collide at the

intersection and lock together. Ignoring any external forces that act on the cars during

the collision, what is the velocity of the cars immediately after the collision?

A) 21.1 m/s in a direction 47.7° east of north

B) 29.7 m/s in a direction 47.7° east of north

C) 21.1 m/s in a direction 52.8° east of north

D) 21.1 m/s in a direction 47.7° west of south

E) 15.1 m/s in a direction 52.8° east of north

35)

Answer: E

9

36) Two automobiles traveling at right angles to each other collide and stick together. Car

A has a mass of 1200 kg and had a speed of 25 m/s before the collision. Car B has a

mass of 1600 kg. The skid marks show that, immediately after the collision, the

wreckage was moving in a direction making an angle of 40° with the original direction

of car A. What was the speed of car B before the collision, assuming that any other

unbalanced forces are negligible?

A) 14 m/s B) 18 m/s C) 11 m/s D) 21 m/s E) 16 m/s

36)

Answer: E

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.

37) A 900-kg car traveling east at 15.0 m/s collides with a 750-kg car traveling

north at 20.0 m/s. The cars stick together. Assume that any other unbalanced

forces are negligible.

(a) What is the speed of the wreckage just after the collision?

(b) In what direction does the wreckage move just after the collision?

37)

Answer: (a) 12.2 m/s (b) 48.0° N of E

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

38) A car heading north collides at an intersection with a truck of the same mass as the car

heading east. If they lock together and travel at 28 m/s at 46° north of east just after the

collision, how fast was the car initially traveling? Assume that any other unbalanced

forces are negligible.

A) 80 m/s B) 20 m/s C) 30 m/s D) 40 m/s

38)

Answer: D

39) Two ice skaters push off against one another starting from a stationary position. The

45.0-kg skater acquires a speed of 0.375 m/s. What speed does the 60.0-kg skater

acquire? Assume that any other unbalanced forces during the collision are negligible.

A) 0.375 m/s

B) 0.750 m/s

C) 0.281 m/s

D) 0.500 m/s

E) 0.000 m/s

39)

Answer:

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