Chapter 8、9、10
Major:
1.
2.
3.
4.
5.
6.
Name:
Identical forces act for the same length of time on two
different masses. The change in momentum of the
smaller mass is (
)
(A) smaller than the change in momentum of the
larger mass, but not zero.
(B) larger than the change in momentum of the larger
mass.
(C) equal to the change in momentum of the larger
mass.
(D) zero.
An elastic collision of two objects is characterized by
the following. (
)
(A) Total momentum of the system is conserved.
(B) Total energy of the system remains constant.
(C) Total kinetic energy of the system remains
constant.
(D) A, B, and C are all true.
An inelastic collision of two objects is characterized
by the following. (
)
(A) Total momentum of the system is conserved.
(B) Total energy of the system remains constant.
(C) Total kinetic energy of the system remains
constant.
(D) Only A and B are true.
A red ball with a velocity of +3.0 m/s collides head-on
with a yellow ball of equal mass moving with a
velocity of -2.0 m/s. What is the velocity of the red
ball after the collision? (
)
(A) zero
(B) -2.0 m/s
(C) +3.0 m/s
(D) +2.5.0 m/s
A 0.140-kg baseball is dropped and reaches a speed of
1.20 m/s just before it hits the ground. It rebounds
with a speed of 1.00 m/s. What is the change of the
ball's momentum? (
)
(A) 0.0280 kg∙m/s upwards
(B) 0.0280 kg∙m/s downwards
(C) 0.308 kg∙m/s upwards
(D) 0.308 kg∙m/s downwards
Two air track carts move along an air track towards
each other. Cart A has a mass of 450g and moves
toward the right with a speed of 0.850m/s and air
track cart B has a mass of 300g and moves toward the
ID No.:
left with a speed of 1.12m/s. What is the total
momentum of the system? (
)
(A) 0.047 kg∙m/s toward the right
(B) 0.719 kg∙m/s toward the right
(C) 0.750 kg∙m/s toward the left
(D) 0.047 kg∙m/s toward the left
7.
A 0.250-kg rubber ball is dropped from a height of
2.00 m. It hits the floor and rebounds to a height of
1.80 m. What is the magnitude of impulse the floor
applies to the ball? (
)
(A) 0.950 N∙s
(B) 0.0804 N∙s
(C) 1.33 N∙s
(D) 3.05 N∙s
8.
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) 40.0N
(B) 107N
(C) 16.7N (D) 26.7N
9.
A 4.00-kg mass and a 9.00-kg mass are being held at
rest against a compressed spring on a frictionless
surface. When the masses are released, the 4.00-kg
mass moves to the east with a speed of 2.00 m/s. What
is the velocity of the 9.00-kg mass after the masses are
released? (
)
(A) 2.00 m/s west
(B) 0.888 m/s west
(C) 0.500 m/s east
(D) 4.50 m/s west
10. A 2.00-kg mass object traveling east at 20.0 m/s
collides with a 3.00-kg mass object traveling west at
10.0 m/s. After the collision, the 2.00-kg mass has a
velocity 5.00 m/s to the west. How much kinetic
energy was lost during the collision? (
)
(A) 458 J
(B) 516 J
(C) 91.7 J
(D) 175 J
11. A 3.00-kg object traveling 20.0 m/s west collides with
a 5.00-kg mass object traveling 12.0 m/s west. The
collision is perfectly elastic, what is the velocity of the
3.00-kg object after the collision? (
)
(A) 20.0 m/s east
(B) 8.00 m/s west
(C) 12.0 m/s east
(D) 10.0 m/s west
12. 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 in a perfectly
inelastic collision 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) 1.200v
(B) 10.0v
(C) 0.900v
(D) 0.800v
13. A 2.00-m rod of negligible mass connects two small
objects. The mass of one object is 1.00 kg and the
other is 1.50 kg. How far is the center of mass of this
system from the 1.00 kg mass? (
)
(A) 0.800 m
(B) 0.670 m
(C) 1.33 m
(D) 1.20 m
14. Two children are riding on a merry-go-round. Child A
is at a greater distance from the axis of rotation than
child B. a) Which child has the larger angular
displacement? (
) b) Which child has the larger
linear displacement? (
) c) Which child has the
larger angular speed? (
) d) Which child has the
larger tangential speed? (
) e) Which child has the
larger centripetal acceleration? (
) f) Which child
has the larger tangential acceleration? (
)
(A) Child A
(B) Child B
(C) They have the same (zero).
(D) They have the same (non-zero).
15. When you ride a bicycle, in what direction is the
angular velocity of the wheels? (
)
(A) to your left
(B) to your right
(C) forwards
(D) backwards
16. If a constant net torque is applied to an object, that
object will (
)
(A) rotate with constant linear velocity.
(B) rotate with constant angular velocity.
(C) rotate with constant angular acceleration.
(D) none of above.
17. A wheel that is rotating at 33.3 rad/s is given an
angular acceleration of 2.15 rad/s2. Through what
angle has the wheel turned when its angular speed
reaches 72.0 rad/s? (
)
(A) 83.2 rad
(B) 316 rad
(C) 697 rad
(D) 948 rad
18. A wrench is acting on a nut. The length of the wrench
lies directly to the east of the nut. A force 150 N acts
on the wrench at a position 15.0 cm from the center of
the nut in a direction 30.0°north of east. What is the
torque about the center of the nut? (
)
(A) 22.5 N∙m
(B) 11.3 N∙m
(C) 19.5 N∙m
(D) 2250 N∙m
19. A person pushes on a doorknob with a force of 5.00 N
perpendicular to the surface of the door. The doorknob
is located 0.800 m from axis of the hinges of the door.
The door begins to rotate with an angular acceleration
of 2.00 rad/s2. What is the moment of inertia of the
door about the hinges? (
)
2
(A) 2.00 kg∙m
(B) 1.00 kg∙m2
(C) 8.00 kg∙m2
(D) 6.40 kg∙m2
20. The moment of inertia of a uniform rod (about its
center) is given by I = ML2/12. What is the kinetic
energy of a 120-cm rod with a mass of 450 g rotating
about its center at 3.60 rad/s? (
)
(A) 0.350 J
(B) 4.20 J
(C) 0.700 J
(D) 0.960 J
21. A thin cylindrical shell is released from rest and rolls
without slipping down an inclined plane that makes an
angle of 30° with the horizontal. How long does it
take it to travel 3.1 m? (
)
(A) 1.4 s
(B) 1.1 s
(C) 2.1 s
(D) 1.6 s
22. A homogeneous cylinder is released from rest and
rolls without slipping down an inclined plane inclined
at 18°to the horizontal. How fast is it moving after it
has rolled 2.2 m down the plane? (
)
(A) 4.3 m/s
(B) 5.2 m/s
(C) 3.0 m/s
(D) 3.7 m/s
23. A figure skater is spinning slowly with arms
outstretched. She brings her arms in close to her body
and her angular speed increases dramatically. The
speed increase is a demonstration of (
)
(A) conservation of kinetic energy: her moment of
inertia is decreased, and so her angular speed must
increase to conserve energy.
(B) conservation of total energy: her moment of
inertia is decreased, and so her angular speed must
increase to conserve energy.
(C) conservation of angular momentum: her moment
of inertia is decreased, and so her angular speed must
increase to conserve angular momentum.
(D) Newton's second law for rotational motion: she
exerts a torque and so her angular speed increases.
24. A figure skater rotating at 5.00 rad/s with arms
extended has a moment of inertia of 2.25 kg∙m2. If the
arms are pulled in so the moment of inertia decreases
to 1.80 kg∙m2, what is the final angular speed? (
)
(A) 2.25 rad/s
(B) 4.60 rad/s
(C) 6.25 rad/s
(D) 1.76 rad/s
25. A force at F   4.00 N  iˆ   3.00 N  ˆj is applied to
an object at position r   2.00m  iˆ   3.00m  ˆj .
What is the torque about the origin? (
)
(A)  8.00 N  m  iˆ   9.00 N  m  ˆj
(B)
 -1.00 N  m  kˆ
(C) 8.00 N  m  iˆ+  9.00 N  m  ˆj
(D)
 -18.00 N  m kˆ
26. A 40.0-kg child running at a speed 3.00 m/s jumps on
a stationary playground merry-go-round at a distance
1.50 m from the axis of rotation of the
merry-go-round. The child is traveling tangential to
the edge of the merry-go-round which has a 600 kg∙m2
moment of inertia about its axis of rotation as she is
running. What is the angular speed of the
merry-go-round after the child jumps on it? (
)
(A) 0.788 rad/s
(B) 0.261 rad/s
(C) 2.00 rad/s
(D) 3.14 rev/s
Write your answer in the table.
1
2
3
4
5
C
D
D
B
C
6
7
8
9
10
A
D
B
B
A
11
12
13
14
15
D
D
D
AADAAA
A
16
17
18
19
20
C
D
B
A
A
21
22
23
24
25
D
C
C
C
D
26
B