##### physics ch 5

1) Point P in the figure indicates the position of an object
traveling at constant speed clockwise

around the circle. Which
arrow best represent the direction the object would travel if the
net

external force on it were suddenly reduced to zero?

D

An object is moving to the right, and experiencing a net force that
is directed to the right. The

magnitude of the force is
decreasing with time. The speed of the object is

A)
increasing.

B) decreasing.

C) constant in time.

A

A stalled car is being pushed up a hill at constant velocity by three
people. The net force on the

car is

A) zero.

B) up the
hill and equal to the weight of the car.

C) down the hill and
equal to the weight of the car.

D) up the hill and greater than
the weight of the car.

E) down the hill and greater than the
weight of the car.

A

4) A 615 N student standing on a scale in an elevator notices that
the scale reads 645 N. From this

information, the student knows
that the elevator must be moving

A) downward.

B)
upward.

C) You cannot tell if it is moving upward or downward.

C

5) A car is being towed at constant velocity on a horizontal road
using a horizontal chain. The

tension in the chain must be equal
to the weight of the car in order to maintain
constant

velocity.

A) True

B) False

B

6) You are standing in a moving bus, facing forward, and you suddenly
fall forward as the bus

comes to an immediate stop. The force
acting on you that causes you to fall forward is

A) the force of
gravity.

B) the normal force due to your contact with the floor
of the bus.

C) the force due to static friction between you and
the floor of the bus.

D) the force due to kinetic friction
between you and the floor of the bus.

E) No forces were acting on
you to cause you to fall.

E

7) Which one of the following free-body diagrams best represents the
free-body diagram, with

correct relative force magnitudes, of a
person in an elevator that is traveling upward with an

unchanging
velocity? F f is the force of the floor on the person and F g is the
force of gravity on

the person.

b

8) Which one of the following free-body diagrams best represents the
free-body diagram, with

correct relative force magnitudes, of a
person in an elevator that is traveling upward but is

gradually
slowing down at a rate of 9 m/s2? F f is the force of the floor on the
person and F g is

the force of gravity on the person.

B

9) A crate is sliding down an inclined ramp at a constant speed of
0.55 m/s. The vector sum of all

the forces acting on this crate
must point down the ramp.

A) True

B) False

B

10) A woman is straining to lift a large crate, without success
because it is too heavy. We denote

the forces on the crate as
follows: P is the upward force the woman exerts on the crate, C is
the

vertical contact force exerted on the crate by the floor, and
W is the weight of the crate. How

are the magnitudes of these
forces related while the woman is trying unsuccessfully to lift
the

crate?

A) P + C = W

B) P + C < W

C) P + C
> W

D) P = C

A

11) Suppose the force of the air drag on an object is proportional to
the speed of the object and in

the direction opposite the
objectʹs velocity. If you throw an object upward, the magnitude of
its

acceleration is greatest

A) right after the object is
released.

B) at the top of its trajectory.

C) The
acceleration of the object is the same throughout the entire trajectory.

a

12) An object is moving forward with a constant velocity. Which
statement about this object

MUST be true?

A) The net force
on the object is zero.

B) The net force on the object is in the
forward direction.

C) No forces are acting on the object.

D)
The acceleration of the object is in the forward direction.

a

13) Suppose you are playing hockey on a new‐age ice surface for which
there is no friction

between the ice and the hockey puck. You
wind up and hit the puck as hard as you can. After

the puck loses
contact with your stick, the puck will

A) start to slow
down.

B) not slow down or speed up.

C) speed up a little,
and then slow down.

D) speed up a little, and then move at a
constant speed.

b

14) A ball is tossed vertically upward. When it reaches its highest
point (before falling back

downward)

A) the velocity is
zero, the acceleration is directed downward, and the force of gravity
acting

on the ball is directed downward.

B) the velocity is
zero, the acceleration is zero, and the force of gravity acting on the
ball is

zero.

C) the velocity is zero, the acceleration is
zero, and the force of gravity acting on the ball is

directed
downward.

D) the velocity and acceleration reverse direction, but
the force of gravity on the ball

remains downward.

E) the
velocity, acceleration, and the force of gravity on the ball all
reverse direction.

A

15) A dog is standing in the bed of a pickup truck. The bed is coated
with ice, causing the force of

friction between the dog and the
truck to be zero. The truck is initially at rest, and
then

accelerates to the right, moving along a flat road. As seen
from a stationary observer (watching

the truck move to the
right), the dog

A) does not move left or right, but the back of
the truck moves towards the dog.

B) moves to the right, but not
as quickly as the truck is moving to the right, causing it
to

slide towards the back of the truck.

C) moves to the
right at the same rate as the truck, so it doesnʹt slide.

D)
moves to the left, as the truck moves to the right, causing the dog to
slide towards the

back of the truck.

a

16) You are seated in a bus and notice that a hand strap that is
hanging from the ceiling hangs

away from the vertical in the
backward direction. From this observation, you can
conclude

that

A) the velocity of the bus is forward.

B)
the velocity of the bus is backward.

C) You cannot conclude
anything about the direction of the velocity of the bus.

c

1) If a 5.0 kg box is pulled simultaneously by a 10.0 N force and a
5.0 N force, then its acceleration

must be

A) 3.0
m/s2.

B) 2.2 m/s2.

C) 1.0 m/s2.

D) We cannot tell from
the information given.

d

2) The figure shows an acceleration-versus-force graph for three
objects pulled by rubber bands.

The mass of object 2 is 36 kg.
What are the masses of objects 1 and 3?

A) 14 kg and 90 kg

B) 72 kg and 18 kg

C) 90 kg and 18
kg

D) 14 kg and 72 kg

A

A 7.0-kg object is acted on by two forces. One of the forces is 10.0
N acting toward the east.

Which of the following forces is the
other force if the acceleration of the object is 1.0 m/s2

toward
the east?

A) 6.0 N east

B) 3.0 N west

C) 12 N
east

D) 9.0 N west

E) 7.0 N west

B

4) An 1100-kg car traveling at 27.0 m/s starts to slow down and comes
to a complete stop in 578

m. What is the magnitude of the average
braking force acting on the car?

A) 690 N

B) 550 N

C)
410 N

D) 340 N

A

5) On its own, a certain tow-truck has a maximum acceleration of 3.0
m/s2. What would be the

maximum acceleration when this truck was
towing a bus of twice its own mass?

A) 2.5 m/s2

B) 2.0
m/s2

C) 1.5 m/s2

D) 1.0 m/s2

D

6) A child on a sled starts from rest at the top of a 15° slope. If
the trip to the bottom takes 15.2 s

how long is the slope? Assume
that frictional forces may be neglected.

A) 293 m

B) 586
m

C) 1130 m

D) 147 m

A

7) The figure shows two forces acting at right angles on an object.
They have magnitudes F1 = 6.3

N and F2 = 2.1 N. What third force
will cause the object to be in equilibrium (acceleration

equals zero)?

A) 6.6 N at 162° counterclockwise from F1

B) 6.6 N at 108°
counterclockwise from F1

C) 4.2 N at 162° counterclockwise from
F1

D) 4.2 N at 108° counterclockwise from F 1

A

8) The figure shows two forces, each of magnitude 4.6 N, acting on an
object. The angle between

these forces is 40°, and they make
equal angles above and below the horizontal. What third

force
will cause the object to be in equilibrium (acceleration equals zero)?

A) 8.6 N pointing to the right

B) 7.0 N pointing to the
right

C) 4.3 N pointing to the right

D) 3.5 N pointing to
the right

A

An object weighing 4.00 N falls from rest subject to a frictional
drag force given by Fdrag =

bv2, where v is the speed of the
object and b = 3.00 N · s2/m2. What terminal speed will
this

object approach?

A) 1.78 m/s

B) 3.42 m/s

C)
1.15 m/s

D) 2.25 m/s

E) 0.75 m/s

c

The figure shows a graph of the acceleration of a 125-g object as a
function of the net force

acting on it. What is the acceleration
at points A and B?

A: 16 m/s^2, B: 4.0 m/s^2

The figure shows a graph of the acceleration of an object as a
function of the net force acting on

it. The mass of this object,
in grams, is closest to

A) 130.

B) 11.

C) 89.

D) 8000.

A

Two forces act on a 55-kg object. One force has magnitude 65 N
directed 59° clockwise from

the positive x-axis, and the other
has a magnitude 35 N at 32° clockwise from the positive

y-axis.
What is the magnitude of this objectʹs acceleration?

A) 1.1
m/s2

B) 1.3 m/s2

C) 1.5 m/s2

D) 1.7 m/s2

A

13) The figure shows two forces acting on an object, with magnitudes
F1 = 78 N and

F2 = 26 N.What third force will cause the object to
be in equilibrium (acceleration equals

zero)?

A) 52 N pointing down

B) 52 N pointing up

C) 82 N pointing
down

D) 82 N pointing up

A

The graph in the figure shows the x component of the acceleration of
a 2.4-kg object as a

function of time (in ms).

(a) At what time(s) does the x component of the net force on the
object reach its maximum

magnitude, and what is that maximum
magnitude?

(b) What is the x component of the net force on the
object at time t = 0.0 ms and at t = 4.0 ms?

Answer: (a) At 3.0 ms, 48 N (b) 12 N, -24 N

15) The graph in the figure shows the net force acting on a 3.0-kg object as a function of time.

(a) What is the acceleration of this object at time t = 2.0
s?

(b) Draw, to scale, a graph of the acceleration of this object
as a function of time over the range

t = 0.00 s to t = 7.0 s.

Answer: (a) 2.0 m/s2

(b) The acceleration-time graph looks the
same as the force-time graph except on the

vertical axis the
numbers (starting at 2.0) are replaced by 0.67, 1.3, 2.0, 2.7, 3.3,
and 4.0.