Chapter
7: KINETIC ENERGY AND WORK

1. Which
of the following is NOT a correct unit for work?

A. erg

B. ft·lb

C. watt

D. newton·meter

E. joule

ans: C

2. Which
of the following groups does NOT contain a scalar quantity?

A.
velocity, force, power

B.
displacement, acceleration, force

C.
acceleration, speed, work

D.
energy, work, distance

E.
pressure, weight, time

ans: B

3. A boy
holds a 40-N weight at arm’s length for 10 s. His arm is 1.5m above
the ground. The work done by the force of the boy on the weight while he is
holding it is:

A. 0

B. 6.1J

C. 40 J

D. 60 J

E. 90 J

ans: A

5. An
object moves in a circle at constant speed. The work done by the centripetal
force is zero

because:

A. the
displacement for each revolution is zero

B. the average
force for each revolution is zero

C. there
is no friction

D. the
magnitude of the acceleration is zero

E. the
centripetal force is perpendicular to the velocity

ans: E

6. An
object of mass 1 g is whirled in a horizontal circle of radius 0.5m at a
constant speed of 2m/s. The work done on the object during one
revolution is:

A. 0

B. 1 J

C. 2 J

D. 4 J

E. 16 J

ans: A (why is this true? asks the professor)

7. The
work done by gravity during the descent of a projectile:

A. is
positive

B. is
negative

C. is
zero

D.
depends for its sign on the direction of the y axis

E.
depends for its sign on the direction of both the x and y axes

ans: A

8. A
baseball is hit high into the upper bleachers of left field. Over its entire
flight the work done by gravity and the work done by air resistance,
respectively, are:

A.
positive; positive

B.
positive; negative

C.
negative; positive

D.
negative; negative

E.
unknown since vital information is lacking

ans: D

9. A line
drive to the shortstop is caught at the same height as it was originally hit.
Over its entire flight the work done by gravity and the work done by air
resistance, respectively, are:

A. zero;
positive

B. zero;
negative

C.
positive; negative

D.
negative; positive

E.
negative; negative

ans: B

10. A
2-kg object is moving at 3m/s. A 4-N force is applied in the
direction of motion and then removed after the object has traveled an
additional 5m. The work done by this force is:

A. 12 J

B. 15 J

C. 18 J

D. 20 J

E. 38 J

ans: D

11. A
sledge (including load) weighs 5000 N. It is pulled on level snow by a dog team
exerting a horizontal force on it. The coefficient of kinetic friction between
sledge and snow is 0.05. How much work is done by the dog team
pulling the sledge 1000m at constant speed?

A. 2.5 × 10^{4} J

B. 2.5 × 10^{5} J

C. 5.0 × 105 J

D. 2.5 × 106 J

E. 5.0 × 106 J

ans: B

12.
Camping equipment weighing 6000N is pulled across a frozen lake by means of a
horizontal rope. The coefficient of kinetic friction is 0.05. The
work done by the campers in pulling the equipment 1000m at constant velocity
is:

A. 3.1 × 104 J

B. 1.5 × 105 J

C. 3.0 × 105 J

D. 2.9 × 106 J

E. 6.0 × 106 J

ans: C

13.
Camping equipment weighing 6000N is pulled across a frozen lake by means of a
horizontal rope. The coefficient of kinetic friction is 0.05. How
much work is done by the campers in pulling the equipment 1000m if its speed is
increasing at the constant rate of 0.20m/s2?

A. −1.2 × 106 J

B. 1.8 × 105 J

C. 3.0 × 105 J

D. 4.2 × 105 J

E. 1.2 × 106 J

ans: D

14. A
1-kg block is lifted vertically 1m by a boy. The work done by the boy is about:

A. depends
on the time taken

B. 1 J

C. 10 J

D. 0.1J

E. zero

ans: C

15. A 0.50-kg
object moves in a horizontal circular track with a radius of 2.5m. An
external force of 3.0N, always tangent to the track, causes the
object to speed up as it goes around. The work done by the external force as
the mass makes one revolution is:

A. 24 J

B. 47 J

C. 59 J

D. 94 J

E. 120 J

ans: B

17. A man
pushes an 80-N crate a distance of 5.0m upward along a
frictionless slope that makes an angle of 30◦
with the horizontal. His force is parallel to the slope. If the speed of
the crate decreases at a rate of 1.5m/s2, then
the work done by the man is:

A. −200 J

B. 61 J

C. 140 J

D. 200 J

E. 260 J

ans: C

18. A man
pushes an 80-N crate a distance of 5.0m upward along a
frictionless slope that makes an angle of 30◦
with the horizontal. The force he exerts is parallel to the slope. If
the speed of the crate is constant, then the work done by the man is:

A. −200 J

B. 61 J

C. 140 J

D. 200 J

E. 260 J

ans: D

19. An
80-N crate slides with constant speed a distance of 5.0m
downward along a rough slope that makes an angle of 30◦ with the horizontal. The work
done by the force of gravity is:

A. −400 J

B. −200 J

C. −69 J

D. 200 J

E. 400 J

ans:
D

20. A man
pulls a sled along a rough horizontal surface by applying a constant force
F at an angle θ above the horizontal. In pulling
the sled a horizontal distance d, the work done by the man is:

A. Fd

B. Fdcos θ

C. Fdsin θ

D. Fd/ cos θ

E. Fd/ sin θ

ans: B

21. A man
wishes to pull a crate 15m across a rough floor by exerting a force of 100 N.
The coefficient of kinetic friction is 0.25. For the man to do the
least work, the angle between the force and the horizontal should be:

A. 0

B. 14◦

C. 43◦

D. 66◦

E. 76◦

ans: A

22. A
particle moves 5m in the positive x direction
while being acted upon by a constant force vector F

= (4N)ˆi + (2 N)ˆj − (4 N)ˆk .
The work done on the particle by this force is:

A. 20 J

B. 10 J

C. −20 J

D. 30 J

E. is
impossible to calculate without knowing other forces

ans:
A

23. A
block is attached to the end of an ideal spring and moved from coordinate xi to
coordinate xf . The
relaxed position is at x = 0. The work done by spring is positive if:

A. xi = 2 cm
and xf = 4cm

B. xi = −2 cm and xf = 4cm

C. xi = −2 cm and xf = −4 cm

D. xi = 2 cm
and xf = −4 cm

E. xi = −4 cm and xf = −2 cm

ans: E

28. An
ideal spring is hung vertically from the ceiling. When a 2.0-kg mass hangs
at rest from it the spring is extended 6.0 cm from its relaxed length. A
downward external force is now applied to the mass to extend the spring an
additional 10 cm. While the spring is being extended by the force, the work
done by the spring is:

A. −3.6J

B. −3.3J

C. −3.4 × 10−5 J

D. 3.3J

E. 3.6J

ans: A

29. An
ideal spring is hung vertically from the ceiling. When a 2.0-kg
block hangs at rest from it the spring is extended 6.0 cm from
its relaxed length. A upward external force is then
applied to the block to move it upward a distance of 16 cm. While the block is
moving upward the work done by the spring is:

A. −1.0J

B. −0.52 J

C. −0.26 J

D. 0.52 J

E. 1.0J

ans: A

30. Which
of the following bodies has the largest kinetic energy?

A. Mass 3M and speed
V

B. Mass 3M and speed
2V

C. Mass 2M and speed
3V

D. Mass M and speed
4V

E. All
four of the above have the same kinetic energy

ans: C

31. Two
trailers, X with mass 500 kg and Y with mass 2000 kg, are being pulled at the
same speed.

The ratio
of the kinetic energy of Y to that of X is:

A. 1:1

B. 2:1

C. 4:1

D. 9:1

E. 1500:1

ans: C

32. A 8000-N car is traveling at 12m/s along a
horizontal road when the brakes are applied. The

car skids to a stop in 4.0 s. How
much kinetic energy does the car lose in this time?

A. 4.8 × 104 J

B. 5.9 × 104 J

C. 1.2 × 105 J

D. 5.8 × 105 J

E. 4.8 × 106 J

ans: B

33. The
velocity of a particle moving along the x axis
changes from vi to vf . For
which values of

vi and vf is the
total work done on the particle positive?

A. vi = 5m/s, vf = 2m/s

B. vi = 5m/s, vf = −2m/s

C. vi = −5m/s, vf = −2m/s

D. vi = −5m/s, vf = 2m/s

E. vi = 2m/s, vf = −5m/s

ans: E

34. An
object is constrained by a cord to move in a circular path of radius 0.5m on a
horizontal

frictionless surface. The cord will break if its tension
exceeds 16 N. The maximum kinetic

energy the object can have is:

A. 4 J

B. 8 J

C. 16 J

D. 32 J

E. 64 J

ans: A

35. The
weight of an object on the moon is one-sixth of its weight on Earth. The ratio
of the

kinetic energy of a body on Earth moving with speed V to that
of the same body moving with

speed V on the moon is:

A. 6:1

B. 36:1

C. 1:1

D. 1:6

E. 1:36

ans: C

36. Which
of the following is the correct combination of dimensions for energy?

A. MLT

B. LT2/m

C. ML2/T2

D. M2L3T

E. ML/T2

ans: C

37. The
amount of work required to stop a moving object is equal to:

A. the
velocity of the object

B. the
kinetic energy of the object

C. the
mass of the object times its acceleration

D. the
mass of the object times its velocity

E. the
square of the velocity of the object

ans: B

38. A 5.0-kg cart
is moving horizontally at 6.0m/s. In
order to change its speed to 10.0m/s, the

net work done on the cart must be:

A. 40 J

B. 90 J

C. 160 J

D. 400 J

E. 550 J

ans: C

41. A
4-kg cart starts up an incline with a speed of 3m/s and
comes to rest 2m up the incline.

The total
work done on the car is:

A. 6 J

B. 8 J

C. 12 J

D. 18 J

E. impossible
to calculate without more information

ans: D

42. Two
objects with masses of m1 and m2 have the
same kinetic energy and are both moving to

the right. The same constant force
F is applied to the left to both masses. If m1 = 4m2, the

ratio of the stopping distance of m1 to that
of m2 is:

A. 1:4

B. 4:1

C. 1:2

D. 2:1

E. 1:1

ans: E

43. A
Boston Red Sox baseball player catches a ball of mass m that is
moving toward him with

speed v. While bringing the ball to
rest, his hand moves back a distance d. Assuming constant

deceleration, the horizontal force exerted on the ball by
his hand is:

A. mv/d

B. mvd

C. mv2/d

D. 2mv/d

E. mv2/(2d)

ans: E

44. A 0.50-kg
object moves on a horizontal circular track with a radius of 2.5m. An
external force

of 3.0N, always tangent to the track,
causes the object to speed up as it goes around. If it

starts from rest its speed at the end of one revolution
is:

A. 9.8m/s

B. 14m/s

C. 15m/s

D. 19m/s

E. 21m/s

ans: B

45. A 0.50-kg
object moves on a horizontal frictionless circular track with a radius of 2.5m. An

external force of 3.0N, always tangent to the
track, causes the object to speed up as it goes

around. If it starts from rest, then at the end of one
revolution the radial component of the

force of the track on it is:

A. 19N

B. 38N

C. 47N

D. 75N

E. 96N

ans: B

46. A
2-kg block is attached to a horizontal ideal spring with a spring constant of
200N/m. When

the spring has its equilibrium length the block is
given a speed of 5m/s. What is the maximum

elongation of the spring?

A. 0

B. 0.05m

C. 5m

D. 10m

E. 100m

ans: C

47. At
time t = 0 a particle starts moving along the x axis. If
its kinetic energy increases uniformly

with t the net force acting on it must
be:

A.
constant

B.
proportional to t

C.
inversely proportional to t

D.
proportional to √t

E.
proportional to 1/√t

ans: E

50. A 1.5-kg
crate falls from a height of 2.0m onto an industrial spring
scale with a spring constant

of 1.5 × 105 N/m. At its
greatest compression the reading on the scale is:

A. 15N

B. 30N

C. 1.5 × 103 N

D. 2.1 × 103 N

E. 3.0 × 103 N

ans: E

53. In
raising an object to a given height by means of an inclined plane, as compared
with raising

the object vertically, there is a reduction in:

A. work
required

B.
distance pushed

C.
friction

D. force
required

E. value
of the acceleration due to gravity

ans: D

54. A
watt is:

A. kg · m/s3

B. kg · m2/s

C. kg · m2/s3

D. kg · m/s

E. kg · m2/s2

ans: C

55. Power
has the dimensions of:

A. ML2/T2

B. MT/L2

C. ML/T2

D. ML2/T3

E. none
of these

ans: D

56. Which
of the following five units represents a quantity that is NOT the same as the
other four?

A. joule

B. erg

C. watt

D. foot·pound

E. newton·meter

ans: C

57. Which
of the following five quantities is NOT an expression for energy? Here m is a
mass,

g is the acceleration due to gravity, h and d are
distances, F is a force, v is a speed, a is an

acceleration, P is power,
and t is time.

A. mgh

B. Fd

C. 1/2mv2

D. ma

E. Pt

ans: D

58. A
watt·second is a unit of:

A. force

B. power

C.
displacement

D. speed

E. energy

ans:
E

59. A
watt per hour is a unit of:

A. energy

B. power

C. force

D.
acceleration

E. none
of these

ans: E

60. A
kilowatt·hour is a unit of:

A. power

B.
energy/time

C. work

D.
power/time

E.
force/distance

ans: C

62. A
woman lifts a barbell 2.0m in 5.0 s. If she lifts it the
same distance in 10 s, the work done

by her is:

A. four
times as great

B. two
times as great

C. the
same

D. half
as great

E.
one-fourth as great

ans: C

64. A
person holds an 80-N weight 2m above the floor for 30 seconds. The power
required to do

this is:

A. 80W

B. 40W

C. 20W

D. 10W

E. none
of these

ans: E

65. A
50-N force is the only force on a 2-kg object that starts from rest. When the
force has been

acting for 2 s the rate at which it is doing work is:

A. 75W

B. 100W

C. 1000W

D. 2500W

E. 5000W

ans: D

66. A
50-N force is the only force a 2-kg crate that starts from rest. At the instant
the object has

gone 2m the rate at which the force is doing work is:

A. 2.5W

B. 25W

C. 75W

D. 100W

E. 500W

ans: E

67. A
particle starts from rest and is acted on by a net force that does work at a
rate that is proportional to the time t. The speed of the
particle is proportional to:

A. √t

B. t

C. t2

D. 1/√t

E. 1/t

ans: A

Chapter
8: POTENTIAL ENERGY AND CONSERVATION OF ENERGY

1. Only
if a force on a particle is conservative:

A. is its
work zero when the particle moves exactly once around any closed path

B. is its
work always equal to the change in the kinetic energy of the particle

C. does
it obey

D. does
it obey

E. is it
not a frictional force

ans: A

2. A
nonconservative force:

A.
violates

B.
violates

C. cannot
do any work

D. must
be perpendicular to the velocity of the particle on which it acts

E. none
of the above

ans: E

3. The
sum of the kinetic and potential energies of a system of objects is conserved:

A. only
when no external force acts on the objects

B. only
when the objects move along closed paths

C. only
when the work done by the resultant external force is zero

D. always

E. none
of the above

ans: E

4. A
force on a particle is conservative if:

A. its
work equals the change in the kinetic energy of the particle

B. it
obeys

C. it
obeys

D. its
work depends on the end points of every motion, not on the path between

E. it is
not a frictional force

ans: D

5. Two
particles interact by conservative forces. In addition, an external force acts
on each particle. They complete round trips, ending at the points where they
started. Which of the following must have the same values at the beginning and
end of this trip?

A. the
total kinetic energy of the two-particle system

B. the
potential energy of the two-particle system

C. the
mechanical energy of the two-particle system

D. the
total linear momentum of the two-particle system

E. none
of the above

ans: B

6. Two
objects interact with each other and with no other objects. Initially object A
has a speed of 5m/s and object B has a speed of 10m/s. In the
course of their motion they return to their initial positions. Then A has a
speed of 4m/s and B has a speed of 7m/s. We can conclude:

A. the
potential energy changed from the beginning to the end of the trip

B.
mechanical energy was increased by nonconservative forces

C.
mechanical energy was decreased by nonconservative forces

D.
mechanical energy was increased by conservative forces

E.
mechanical energy was decreased by conservative forces

ans: C

7. A good
example of kinetic energy is provided by:

A. a
wound clock spring

B. the
raised weights of a grandfather’s clock

C. a
tornado

D. a
gallon of gasoline

E. an
automobile storage battery

ans: C

8. No
kinetic energy is possessed by:

A. a
shooting star

B. a
rotating propeller on a moving airplane

C. a
pendulum at the bottom of its swing

D. an
elevator standing at the fifth floor

E. a cyclone

ans: D

9. The
wound spring of a clock possesses:

A.
kinetic but no potential energy

B.
potential but no kinetic energy

C. both
potential and kinetic energy in equal amounts

D. neither
potential nor kinetic energy

E. both
potential and kinetic energy, but more kinetic energy than potential energy

ans: B

10. A
body at rest in a system is capable of doing work if:

A. the
potential energy of the system is positive

B. the
potential energy of the system is negative

C. it is
free to move in such a way as to decrease its kinetic energy

D. it is
free to move in such a way as to decrease the potential energy of the system

E. it is
free to move in such a way as to increase the potential energy of the system

ans: D

11. Which
one of the following five quantities CANNOT be used as a unit of potential
energy?

A. watt·second

B. gram·cm/s2

C. joule

D. kg·m2/s2

E. ft·lb

ans: B

12.
Suppose that the fundamental dimensions are taken to be: force (F), velocity
(V) and time (T). The dimensions of potential energy
are then:

A. F/T

B. FVT

C. FV/T

D. F/T2

E. FV2/T2

ans: B

14. A
golf ball is struck by a golf club and falls on a green three meters above the
tee. The potential

energy of the Earth-ball system is greatest:

A. just
before the ball is struck

B. just
after the ball is struck

C. just
after the ball lands on the green

D. when
the ball comes to rest on the green

E. when
the ball reaches the highest point in its flight

ans: E

16. A 6.0-kg
block is released from rest 80m above the ground. When it has fallen 60m its kinetic

energy is approximately:

A. 4800 J

B. 3500 J

C. 1200 J

D. 120 J

E. 60 J

ans: B

17. A
2-kg block is thrown upward from a point 20m above Earth’s surface. At what
height above Earth’s surface will the gravitational potential energy of the
Earth-block system have increased by 500 J?

A. 5m

B. 25m

C. 46m

D. 70m

E. 270m

ans: C

18. An
elevator is rising at constant speed. Consider the following statements:

II. the kinetic energy of the elevator is constant

III. the gravitational potential energy of the Earth-elevator
system is constant

IV. the acceleration of the elevator is zero

V. the
mechanical energy of the Earth-elevator system is constant

A. all
five are true

B. only
II and V are true

C. only
IV and V are true

D. only
I, II, and III are true

E. only
I, II, and IV are true

ans: E

19. A
projectile of mass 0.50 kg is fired with an initial speed of 10m/s at an
angle of 60◦ above the horizontal. The
potential energy of the projectile-Earth system (relative potential energy when
the projectile is at ground level) is:

A. 25 J

B. 18.75 J

C. 12.5J

D. 6.25 J

E. none
of these

ans: B

21. A 2.2-kg
block starts from rest on a rough inclined plane that makes an angle of 25◦ with the horizontal. The
coefficient of kinetic friction is 0.25. As the block goes 2.0m down
the plane the mechanical energy of the Earth-block system changes by:

A. 0

B. −9.8J

C. 9.8J

D. −18 J

E. 18 J

ans: B

24. A
particle moves along the x axis under the influence of a stationary
object. The net force on the particle is given by F = (8N/m3)x3. If the potential energy is taken to be zero for x = 0 then
the potential energy is given by:

A. (2 J/m4)x4

B. (−2J/m4)x4

C. (24 J/m2x2

D. (−24 J/m2)x2

E. 5 J −
(2 J/m4)x4

ans:
B

25. A 0.20-kg
particle moves along the x axis under the influence of a stationary
object. The potential energy is given by U(x) = (8.0J/m2)x2 + (2.0J/m4)x4 ,

where x is in coordinate of the particle.
If the particle has a speed of 5.0m/s when it
is at

x = 1.0m, its
speed when it is at the origin is:

A. 0

B. 2.5m/s

C. 5.7m/s

D. 7.9m/s

E. 11m/s

ans: E

27. A
force of 10N holds an ideal spring with a 20-N/m spring constant in
compression. The potential energy stored in the spring is:

A. 0.5J

B. 2.5J

C. 5 J

D. 10 J

E. 200 J

ans: B

28. An
ideal spring is used to fire a 15.0-g pellet horizontally.
The spring has a spring constant of 20N/m and is initially
compressed by 7.0 cm. The kinetic energy of the pellet as it
leaves the spring is:

A. zero

B. 2.5 × 10−2 J

C. 4.9 × 10−2 J

D. 9.8 × 10−2 J

E. 1.4J

ans: C

29. A 0.50-kg
block attached to an ideal spring with a spring constant of 80N/m
oscillates on a horizontal frictionless surface. The total mechanical energy is
0.12 J. The greatest extension of the spring from its equilibrium length
is:

A. 1.5 × 10−3 m

B. 3.0 × 10−3 m

C. 0.039m

D. 0.054m

E. 18m

ans: D

30. A 0.50-kg block
attached to an ideal spring with a spring constant of 80N/m
oscillates on a horizontal frictionless surface. The total mechanical energy is
0.12 J. The greatest speed of the block is:

A. 0.15m/s

B. 0.24m/s

C. 0.49m/s

D. 0.69m/s

E. 1.46m/s

ans: D

31. A 0.50-kg
block attached to an ideal spring with a spring constant of 80N/m
oscillates on a horizontal frictionless surface. When the spring is 4.0 cm
longer than its equilibrium length, the speed of the block is 0.50m/s. The
greatest speed of the block is:

A. 0.23m/s

B. 0.32m/s

C. 0.55m/s

D. 0.71m/s

E. 0.93m/s

ans: D

32. A 0.5-kg
block slides along a horizontal frictionless surface at 2m/s. It is
brought to rest by compressing a very long spring of spring constant 800N/m. The
maximum spring compression is:

A. 0

B. 3 cm

C. 5 cm

D. 80 cm

E. 80m

ans: C

34. A
700-N man jumps out of a window into a fire net 10m below. The net stretches 2m
before bringing the man to rest and tossing him back into the air. The maximum
potential energy of the net, compared to its unstretched potential energy, is:

A. 300 J

B. 710 J

C. 850 J

D. 7000 J

E. 8400 J

ans: E

60. A
5-kg projectile is fired over level ground with a velocity of 200m/s at an
angle of 25◦ above the horizontal. Just before
it hits the ground its speed is 150m/s. Over the entire trip
the change in the internal energy of the projectile and air is:

A. +19, 000 J

B. −19, 000 J

C. +44, 000 J

D. −44, 000 J

E. 0

ans: C

61. A 0.75-kg
block slides on a rough horizontal table top. Just before it hits a horizontal
idea spring its speed is 3.5m/s. It
compresses the spring 5.7 cm before coming to rest. If the spring constant
is 1200N/m, the internal energy of the block and the table top must have:

A. not
changed

B.
decreased by 1.9J

C.
decreased by 2.6J

D.
increased by 1.9J

E.
increased by 2.6J

ans: C

Chapter
9: CENTER OF MASS AND LINEAR MOMENTUM

1. Which
one of the following statements is true?

A. the
center of mass of an object must lie within the object

B. all
the mass of an object is actually concentrated at its center of mass

C. the
center of mass of an object cannot move if there is zero net force on the
object

D. the
center of mass of a cylinder must lie on its axis

E. none
of the above

ans: E

3. The
center of mass of a uniform disk of radius R is
located:

A. on the
rim

B. a
distance R/2 from the center

C. a
distance R/3 from the center

D. a
distance 2R/3 from the center

E. at the
center

ans: E

4. The
center of mass of the system consisting of Earth, the Sun, and the planet Mars
is:

A. closer
to Earth than to either of the other bodies

B. closer
to the Sun than to either of the other bodies

C. closer
to Mars than to either of the other bodies

D. at the
geometric center of the triangle formed by the three bodies

E. at the
center of the line joining Earth and Mars

ans: B

5. The
center of mass of Earth’s atmosphere is:

A. a
little less than halfway between Earth’s surface and the outer boundary of the
atmosphere

B. near
the surface of Earth

C. near
the outer boundary of the atmosphere

D. near
the center of Earth

E. none
of the above

ans: D

8. Block
A, with a mass of 4 kg, is moving with a speed of 2.0m/s while
block B, with a mass of 8 kg, is moving in the opposite direction with a speed
of 3m/s. The center of mass of the two block-system
is moving with a velocity of:

A. 1.3m/s in the same direction as A

B. 1.3m/s in the
same direction as B

C. 2.7m/s in the
same direction as A

D. 1.0m/s in the
same direction as B

E. 5.0m/s in the
same direction as A

ans: B

9. At the
same instant that a 0.50-kg ball is dropped from 25m above Earth, a
second ball, with a mass of 0.25 kg, is thrown straight upward
from Earth’s surface with an initial speed of 15m/s. They
move along nearby lines and pass each other without colliding. At the end of 2.0 s the height
above Earth’s surface of the center of mass of the two-ball system is:

A. 2.9m

B. 4.0m

C. 5.0m

D. 7.1m

E. 10.4m

ans: D

16. A man
sits in the back of a canoe in still water. He then moves to the front of the
canoe and

sits there. Afterwards the canoe:

A. is
forward of its original position and moving forward

B. is
forward of its original position and moving backward

C. is
rearward of its original position and moving forward

D. is
rearward of its original position and moving backward

E. is
rearward of its original position and not moving

ans: E

21. A 2.0-kg
block is attached to one end of a spring with a spring constant of 100N/m and a

4.0-kg
block is attached to the other end. The blocks are placed on a horizontal
frictionless

surface and set into motion. At one instant the 2.0-kg
block is observed to be traveling to the

right with a speed of 0.50m/s and the
4.0-kg block is observed to be traveling to the left with

a speed of 0.30m/s. Since
the only forces on the blocks are the force of gravity, the normal

force of the surface, and the force of the spring, we
conclude that:

A. the
spring is compressed at the time of the observation

B. the
spring is not compressed at the time of observation

C. the
motion was started with the masses at rest

D. the
motion was started with at least one of masses moving

E. the
motion was started by compressing the spring

ans: D

22. A 2.0-kg mass
is attached to one end of a spring with a spring constant of 100N/m and a 4.0-kg mass
is attached to the other end. The masses are placed on a horizontal frictionless
surface and the spring is compressed 10 cm. The spring is then released with
the masses at rest and the masses oscillate. When the spring has its
equilibrium length for the first time the 2.0-kg mass has a speed of 0.36m/s. The
mechanical energy that has been lost to the instant is:

A. zero

B. 0.31 J

C. 0.61 J

D. 0.81 J

E. 1.2J

ans: B

23.
Momentum may be expressed in:

A. kg/m

B. gram·s

C. N·s

D. kg/(m·s)

E. N/s

ans: C

24. The
momentum of an object at a given instant is independent of its:

A.
inertia

B. mass

C. speed

D.
velocity

E.
acceleration

ans: E

25. Two
bodies, A and B, have equal kinetic energies. The mass of A is nine times that
of B. The

ratio of the momentum of A to that of B is:

A. 1:9

B. 1:3

C. 1:1

D. 3:1

E. 9:1

ans: D

26. Two
objects, P and Q, have the same momentum. Q has more kinetic energy than P if
it:

A. weighs
more than P

B. is
moving faster than P

C. weighs
the same as P

D. is
moving slower than P

E. is
moving at the same speed as P

ans: B

27. A
particle moves along the x axis. Its momentum is graphed below as a
function of time. Rank

the numbered regions according to the magnitude of the
force acting on the particle, least to

greatest.

28. A 1.0-kg ball
moving at 2.0m/s perpendicular to a wall rebounds from the wall at 1.5m/s.

The
change in the momentum of the ball is:

A. zero

B. 0.5N · s away
from wall

C. 0.5N · s toward
wall

D. 3.5N · s away
from wall

E. 3.5N · s toward
wall

ans: D

29. If
the total momentum of a system is changing:

A.
particles of the system must be exerting forces on each other

B. the
system must be under the influence of gravity

C. the
center of mass must have constant velocity

D. a net
external force must be acting on the system

E. none
of the above

ans: D

30. When
you step on the accelerator to increase the speed of your car, the force that
accelerates

the car is:

A. the
force of your foot on the accelerator

B. the
force of friction of the road on the tires

C. the
force of the engine on the drive shaft

D. the
normal force of the road on the tires

E. none
of the above

ans: B

31. A 2.5-kg
stone is released from rest and falls toward Earth. After 4.0 s, the
magnitude of its

momentum is:

A. 98 kg · m/s

B. 78 kg · m/s

C. 39 kg · m/s

D. 24 kg · m/s

E. zero

ans: A

32. A
64-kg woman stands on frictionless level ice with a 0.10-kg
stone at her feet. She kicks the

stone with her foot so that she acquires a velocity of 0.0017m/s in the
forward direction. The

velocity acquired by the stone is:

A. 1.1m/s forward

B. 1.1m/s
backward

C. 0.0017m/s forward

D. 0.0017m/s
backward

E. none
of these

ans: B

33. A man
is marooned at rest on level frictionless ice. In desperation, he hurls his
shoe to the

right at 15m/s. If the man weighs 720N
and the shoe weighs 4.0N, the man moves to the left

with a speed of:

A. 0

B. 2.1 × 10−2 m/s

C. 8.3 × 10−2 m/s

D. 15m/s

E. 2.7 × 103 m/s

ans: C

34. Two
spacemen are floating together with zero speed in a gravity-free region of
space. The mass

of spaceman A is 120 kg and that of spaceman B is 90
kg. Spaceman A pushes B away from

him with B attaining a final speed of 0.5m/s. The
final recoil speed of A is:

A. zero

B. 0.38m/s

C. 0.5m/s

D. 0.67m/s

E. 1.0m/s

ans: B

35. A
projectile in flight explodes into several fragments. The total momentum of the
fragments

immediately after this explosion:

A. is the
same as the momentum of the projectile immediately before the explosion

B. has
been changed into kinetic energy of the fragments

C. is
less than the momentum of the projectile immediately before the explosion

D. is
more than the momentum of the projectile immediately before the explosion

E. has
been changed into radiant energy

ans: A

36. A
rifle of mass M is initially at rest but free to recoil. It fires a bullet of
mass m and velocity

v (relative to the ground). After firing, the
velocity of the rifle (relative to the ground) is:

A. −mv

B. −Mv/m

C. −mv/M

D. −v

E. mv/M

ans: C

37.
Bullets from two revolvers are fired with the same velocity. The bullet from
gun #1 is twice as

heavy as the bullet from gun #2. Gun #1 weighs three
times as much as gun #2. The ratio

of the momentum imparted to gun #1 to that imparted
to gun #2 is:

A. 2:3

B. 3:2

C. 2:1

D. 3:1

E. 6:1

ans: C

39.
Force:

A. equals
the negative integral (with respect to distance) of the potential energy
function

B. is the
ability to do work

C. is the
rate of change of doing work

D. equals
the time rate of change of momentum

E. has
dimensions of momentum multiplied by time

ans: D

40. Cart
A, with a mass of 0.20 kg, travels on a horizontal air track at 3.0m/s and
hits cart B,

which has a mass of 0.40 kg and is initially
traveling away from A at 2.0m/s. After
the collision

the center of mass of the two cart system has a speed
of:

A. zero

B. 0.33m/s

C. 2.3m/s

D. 2.5m/s

E. 5.0m/s

ans: B

42. A
cart loaded with sand slides forward along a horizontal frictionless track. As
the cart moves,

sand trickles out at a constant rate through a hole in
the back of the cart. The acceleration of

the cart is:

A.
constant and in the forward direction

B.
constant and in the backward direction

C.
variable and in the forward direction

D.
variable and in the backward direction

E. zero

ans: E

47. The
physical quantity “impulse” has the same dimensions as that of:

A. force

B. power

C. energy

D.
momentum

E. work

ans: D

48. The
law of conservation of momentum applies to a system of colliding objects only
if:

A. there
is no change in kinetic energy of the system

B. the
coefficient of restitution is one

C. the
coefficient of restitution is zero

D. the
net external impulse is zero

E. the
collisions are all elastic

ans: D

49.
Sphere X, of mass 2 kg, is moving to the right at 10m/s. Sphere
Y, of mass 4 kg, is moving to

the left at 10m/s. The two spheres collide
head-on. The magnitude of the impulse of X on Y

is:

A. twice
the magnitude of the impulse of Y on X

B. half
the magnitude of the impulse of Y on X

C.
one-fourth the magnitude of the impulse of Y on X

D. four times the magnitude of the impulse of Y on X

E. the
same as the magnitude of the impulse of Y on X

ans: E

50. Two
bodies of unequal mass, placed at rest on a frictionless surface, are acted on
by equal

horizontal forces for equal times. Just after these forces
are removed, the body of greater mass

will have:

A. the
greater speed

B. the
greater acceleration

C. the
smaller momentum

D. the
greater momentum

E. the
same momentum as the other body

ans: E

51. A 0.2-kg
rubber ball is dropped from the window of a building. It strikes the sidewalk
below

at 30m/s and rebounds up at 20m/s. The
impulse on the ball during the collision is:

A. 10N · s upward

B. 10N · s
downward

C. 2.0N · s upward

D. 2.0N · s
downward

E. 9.8N · s upward

ans: A

52. A
10-kg block of ice is at rest on a frictionless horizontal surface. A 1.0-N force
is applied in

an easterly direction for 1.0 s.
During this time interval, the block:

A.
acquires a speed of 1m/s

B. moves
10 cm

C.
acquires a momentum of 1.0kg · m/s

D.
acquires a kinetic energy of 0.1J

E. none
of the above

ans: C

54. What
magnitude impulse will give a 2.0-kg object a momentum change of
magnitude + 50 kg · m/s?

A. +25N · s

B. −25N · s

C. +50N · s

D. −50N · s

E. +100N · s

ans: C

55. A
student’s life was saved in an automobile accident because an airbag expanded
in front of

his head. If the car had not been equipped with an
airbag, the windshield would have stopped

the motion of his head in a much shorter time.
Compared to the windshield, the airbag:

A. causes
a much smaller change in momentum

B. exerts
a much smaller impulse

C. causes
a much smaller change in kinetic energy

D. exerts
a much smaller force

E. does
much more work

ans: D

59.
Whenever an object strikes a stationary object of equal mass:

A. the
two objects cannot stick together

B. the
collision must be elastic

C. the
first object must stop

D. momentum
is not necessarily conserved

E. none
of the above

ans: E

60. For a two-body collision involving objects with different
masses, a frame of reference which has

the same velocity relative to the laboratory as does
the center of mass of the two objects is:

A. a
frame for which the momentum of the incident object is zero

B. a
frame for which the momentum of the target object is zero

C. a
frame for which the average momentum of the two objects is zero

D. a
frame for which the total momentum of the two objects is zero

E. none
of the above

ans: D

61. An
inelastic collision is one in which:

A.
momentum is not conserved but kinetic energy is conserved

B. total
mass is not conserved but momentum is conserved

C.
neither kinetic energy nor momentum is conserved

D.
momentum is conserved but kinetic energy is not conserved

E. the
total impulse is equal to the change in kinetic energy

ans: D

62. A 4.0-N puck
is traveling at 3.0m/s. It strikes a 8.0-N puck, which is stationary. The two

pucks stick together. Their common final speed is:

A. 1.0m/s

B. 1.5m/s

C. 2.0m/s

D. 2.3m/s

E. 3.0m/s

ans: A

63. A 3.00-g
bullet traveling horizontally at 400m/s hits a 3.00-kg
wooden block, which is initially

at rest on a smooth horizontal table. The bullet
buries itself in the block without passing

through. The speed of the block after the collision is:

A. 1.33m/s

B. 0.40m/s

C. 12.0m/s

D. 40.0m/s

E. 160m/s

ans: B

64. A
2-kg cart, traveling on a horizontal air track with a speed of 3m/s,
collides with a stationary

4-kg cart. The carts stick together. The impulse exerted by
one cart on the other has a

magnitude of:

A. 0

B. 4N · s

C. 6N · s

D. 9N · s

E. 12N · s

ans: B

65. A 3-g
bullet is fired horizontally into a 10-kg block of wood suspended by a rope
from the

ceiling. The block swings in an arc, rising 3mm above its
lowest position. The velocity of the

bullet was:

A.
unknown since the heat generated in the collision was not given

B. 8.0 × 102 m/s

C. 24.0m/s

D. 8.00m/s

E. 2.4 × 104 m/s

ans: B

66. A 3.0-kg and
a 2.0-kg cart approach each other on a horizontal air track. They collide
and

stick together. After the collision their total kinetic
energy is 40 J. The speed of their center

of mass is:

A. zero

B. 2.8m/s

C. 4.0m/s

D. 5.2m/s

E. 6.3m/s

ans: C

67.
Blocks A and B are moving toward each other. A has a mass of 2.0 kg and
a velocity of 50m/s,

while B has a mass of 4.0 kg and
a velocity of −25m/s. They
suffer a completely inelastic

collision. The kinetic energy lost during the collision is:

A. 0

B. 1250 J

C. 3750 J

D. 5000 J

E. 5600 J

ans: C

68. For a
completely inelastic two-body collision the kinetic energy retained by the
objects is the

same as:

A. the
total kinetic energy before the collision

B. the
difference in the kinetic energies of the objects before the collision

C. 1

2Mv2

com, where M is the
total mass and vcom is the velocity of the center of
mass

D. the
kinetic energy of the more massive body before the collision

E. the
kinetic energy of the less massive body before the collision

ans: C

69. A
75-kg man is riding in a 30-kg cart at 2.0m/s. He
jumps off in such a way as to land on the

ground with no horizontal velocity. The resulting change
in speed of the cart is:

A. zero

B. 2.0m/s

C. 3.0m/s

D. 5.0m/s

E. 7.0m/s

ans: D

70. An
elastic collision is one in which:

A.
momentum is not conserved but kinetic energy is conserved

B. total
mass is not conserved but momentum is conserved

C.
kinetic energy and momentum are both conserved

D.
momentum is conserved but kinetic energy is not conserved

E. the
total impulse is equal to the change in kinetic energy

ans: C

71.
Object A strikes the stationary object B head-on in an
elastic collision. The mass of A is fixed,

you may choose the mass of B appropriately. Then:

A. for B
to have the greatest recoil speed, choose mB = mA

B. for B
to have the greatest recoil momentum, choose mB
mA

C. for B
to have the greatest recoil kinetic energy, choose mB
mA

D. for B
to have the least recoil speed, choose mB = mA

E. for B
to have the greatest recoil kinetic energy, choose mB = mA

ans: E

72. Block
A, with a mass of 2.0 kg, moves along the x axis with
a velocity of 5.0m/s in the positive

x direction. It suffers an elastic collision with
block B, initially at rest, and the blocks leave the

collision along the x axis. If
B is much more massive than A, the speed of A after the collision

is:

A. 0

B. +5.0m/s

C. −5.0m/s

D. +10m/s

E. −10m/s

ans: C

73. A
very massive object traveling at 10m/s strikes a very light
object, initially at rest, and the

light object moves off in the direction of travel of the
heavy object. If the collision is elastic,

the speed of the lighter object is:

A. 5.0m/s

B. 10m/s

C. 15m/s

D. 20m/s

E. Can’t
tell from the information given.

ans: D

74.
Sphere A has mass m and is moving with velocity v. It
makes a head-on elastic collision with

a stationary sphere B of mass 2m. After
the collision their speeds (vA and vB) are:

A. 0, v/2

B. −v/3, 2v/3

C. −v, v

D. −2v/3, v/3

E. none
of these

ans: B

75.
Blocks A and B are moving toward each other along the x axis. A
has a mass of 2.0 kg and

a velocity of 50m/s, while B has a mass of 4.0 kg and
a velocity of −25m/s. They
suffer an

elastic collision and move off along the x axis. The
kinetic energy transferred from A to B

during the collision is:

A. 0

B. 2500 J

C. 5000 J

D. 7500 J

E. 10000
J

ans: A

76. When
a particle suffers a head-on elastic collision with another particle, initially
at rest, the

greatest fraction of kinetic energy is transferred if:

A. the
incident particle is initially traveling very fast

B. the
incident particle is traveling very slowly

C. the
incident particle is much more massive than the target particle

D. the
incident particle is much less massive than the target particle

E. the
incident and target particle have the same mass

ans: E

77. Two
objects, X and Y, are held at rest on a horizontal frictionless surface and a
spring is

compressed between them. The mass of X is 2/5 times
the mass of Y. Immediately after the

spring is released, X has a kinetic energy of 50 J and Y
has a kinetic energy of:

A. 20 J

B. 8 J

C. 310 J

D. 125 J

E. 50 J

ans: D

79. Two
identical carts travel at 1m/s in opposite directions on a
common horizontal surface. They

collide head-on and are reported to rebound, each with a
speed of 2m/s. Then:

A.
momentum was not conserved; therefore, the report must be false

B. if
some other form of energy were changed to kinetic during the collision, the
report could

be true

C. if the
collision were elastic, the report could be true

D. if
friction were present, the report could be true

E. if the
duration of the collision were long enough, the report could be true

ans: B

80. A
block moves at 5.0m/s in the positive x direction
and hits an identical block, initially at

rest. A small amount of gunpowder had been placed on
one of the blocks. The explosion does

not harm the blocks but it doubles their total kinetic
energy. After the explosion the blocks

move along the x axis and
the incident block has a speed in of:

A. 1.8m/s

B. 5.0m/s

C. 6.8m/s

D. 7.1m/s

E. 11.8m/s

ans:
A