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South Pasadena  A.P. Physics
Chapter 4
Name________________________________
Newton’s Laws  Practice Test
True/False
___ 1. Aristotle believed that the natural state of a
body was at rest and that a force was necessary
to keep a body in motion.
13. A 4.0-kilogram mass has how much inertia
compared to a 2-kilogram object?
a) 2x the inertia
___ 2. Aristotle also believed that it was “natural” for
heavy things to fall and light things to rise.
b) ½ the inertia
c) 1/9.8 the inertia
___ 3. Galileo was concerned about how things
move, while Newton was concerned about why
things moved.
___ 4. Galileo also believed like Aristotle that “a
force” is needed keep an object moving.
___ 5. Frictional force is proportional to a normal
force acting on an object.
d) 9.8 x the inertia
14. If a steel ball is rolled alongside a circular
tubing on a flat table, what would be the path of
the steel ball after leaving the boundary of
the circular tubing? Draw the path that it
would take!
Matching:
Use either Galileo Galilei (G) or
Isaac Newton (N)
___6.
Studied Dynamics
___7.
Lived 1642-1727.
___8.
Lived 1564-1642.
___9.
Studied Kinematics
10.
c) quadrupled
d) unchanged
b) a softball in flight
c) a seated high school
student
a) 1.0 kg
b) 5.0 kg
Does a 2-kilogram bunch of bananas, have twice
the weight, as a 1-kg bunch of bananas when
weighed in the same location? __________
18.
You are in outer space and you throw the 2kilogram mass away from your spacecraft;
describe the motion of the object and your
motion. ________________________________
_______________________________________
_______________________________________
19.
If you are standing on a moving bus and you
drop a coin to the floor, how will the coin fall,
relative to the ground outside? ______________
_______________________________________
_______________________________________
Which object has the greatest inertia?
a) a 5.00 kg mass moving at 10.0 m/s
c) a 15.0 kg mass moving at 10.0 m/s
d) a 20.0 kg mass moving at 1.0 m/s
c) 6.0 kg
d) 7.0 kg
17.
d) a rising helium
filled toy balloon
b) a 10.0 kg mass moving at 1.0 m/s
c) 9.81 N
d) 19.6 N
16. The mass of an object whose weight is 9.8 N is?
Which object has the greatest inertia?
a) a falling leaf
12.
a) 4.91 N
b) 2.00 N
A 0.50-kilogram cart is rolling at a speed of
0.40 meters per second. If the speed of the cart
is doubled, the inertia of the cart is
a) halved
b) doubled
11.
15. The weight of a 2-kilogram object on the surface
of the Earth is
20.
Which diagram represents a box in equilibrium
(having a net force of zero)?
a) 5 N
Box
5N
22.
Mass is a measure of the amount of
_________ in an object.
23.
Volume is the amount of _________that an
object occupies.
24.
Weight is a measure of the amount of
________ ____ ___ _________ on an object.
5N
25. If the sum of all the forces acting on a moving
object is zero, the object will
2N
b) 5 N
Box
5N
a) slow down and stop
b) change the direction of its motion
c) accelerate uniformly
2N
d) continue moving with constant velocity
2N
c)
2N
Box
26. A force of 25 N east and a force of 25 N west act
concurrently on a 5-kilogram cart. Find the
acceleration of the cart.
2N
a) 1.0 m/s2 west
b) 0.20 m/s2 east
5N
c) 5.0 m/s2 east
d) 0 m/s2
d) 5 N
Box
3N
27. Draw a free body diagram of the cart in the
previous question (of all of the forces acting):
2N
21.
What are the net forces in the four problems in
the box below?
Applied Forces
5 N East and 10 N East
Net Force
=?
28. An object has a weight of 4.5 N and is sitting on a
table. What is the value for the normal force?
____________
Its direction is pointing _____
5 N West and 10 N East
5 N East and 5 N West
5 N East and 8 N South
29. If you have a mass of 60 kilograms and a weight
of 120 pounds on the Earth, what will be your
mass and weight on the moon (where gravity is 6
times less than on Earth?
Mass on Moon =
__________
Weight on Moon =
__________
30. If an object is 2.0 N on the earth (Object A) and
another object is 2.0 N on the moon (Object B),
which one has a greater mass?
a) Object A
36. A cardboard box of mass m on a wooden floor is
represented by the free body diagram below:
+y
b) Object B
FN
F app
+x
31. Which object has greater weight on the earth?
a) Object A
mg
b) Object B
32. A 0.15-kilogram baseball moving at 20 m/s is
stopped by a catcher in 0.010 seconds. The
average force stopping the ball is
Given the FBD, which of the following
expressions could be accurate mathematical
representations for the box? Choose all that apply.
a) FN – mg = m ax
b) −F app = m ax
a) 3.0 x 10
-2
N
c) FN – mg = m ay
0
b) 3.0 x 10 N
d) F app = m ay
d) 3.0 x 10 1 N
d) 3.0 x 10 2 N
33. Two forces, F1 and F2, are applied to a block on a
frictionless, horizontal surface as shown below.
F1 = 12.0 N
37. Three objects with differing masses are connected
by strings and pulled by the right most string with
Tension T1 across a frictionless surface as shown
in the diagram below.
F2 = 2.0 N
T3
Block
//////////////////////////////////////////
Frictionless Surface
If the magnitude of the block’s acceleration is 2.0
m/s2, what is the mass of the block?
a) 1.0 kg
c) 6.0 kg
b) 5.0 kg
d) 7.0 kg
m
2m
T2
3m
T1
Which of the following expressions accurately depicts
the acceleration of the system? Choose all that apply.
a) T3/2m
b) T2/3m
c) T1/6m
34. A 25- N horizontal force northward and a 35-N
horizontal force southward act concurrently on a
15-kg object on a frictionless surface. What is the
magnitude of the object’s acceleration?
a) 0.67 m/s2
c) 2.3 m/s2
2
b) 1.7 m/s
d) 4.0 m/s2
35. A girl whose weight is 200 N hangs from a bar
supported by two strands of rope. What is the
tension in each strand of rope?
a) 400 N
c) 200 N
b) 300 N
d) 100 N
d) None of the above.
38. An object that is moving, must have at least ?
force(s) acting on it.
a) 0
b) 1
c) 2
d) 4
39. The acceleration of an object is inversely
proportional to the
a) force on the object.
c) velocity of the object.
b) mass of the object.
d) None of these.
40. A 20 N force due north and a 20 N force due east
act concurrently on an object as shown in the
diagram below.
North
45. Which body is in equilibrium?
a) a satellite orbiting Earth in a circular orbit.
b) a ball falling freely toward the surface of Earth.
c) a car moving with constant speed along a
straight, level road.
20. N
d) a projectile at the highest point in its trajectory.
East
20. N
The additional force necessary to bring the object
into a state of equilibrium is
a) 20. N northeast
c) 28 N northeast
b) 20. N southwest
d) 28 N southwest
41. A 3 N force and a 4 N force are acting
concurrently on a point. Which force could not
produce equilibrium with these two forces?
a) 1 N
c) 9 N
b) 7 N
d) 4 N
42. A net force of 10. N accelerates an object at 5.0
m/s2. What net force would be required to
accelerate the same object at 1.0 m/s2?
a) 1.0 N
c) 5.0 N
b) 2.0 N
d) 50. N
46. A 15 kg wagon is pulled to the right across a
surface by a tension of 100 N at an angle of 30
degrees above the horizontal. A frictional force of
20 N to the left acts simultaneously. What is the
acceleration of the wagon? _____
100 N
30
Ff
15 kg
47. A traffic light is suspended by two cables as shown
in the diagram. If cable 1 has a tension T1 = 49 N
and cable 2 has a tension T2 = 85 N, find the mass
of the traffic light.
30
60
T1
T2
43. A 1.0 N metal disk rests on an index card that is
balanced on top of a glass. What is the net force
acting on the disk?
a) 1 N
metal disk
b) 2 N
c) 0 N
d) 9.8 N
glass
index card
44. A 1200 kg space vehicle travels at 4.8 m/s along a
level surface of Mars. If the magnitude of the
gravitational field strength on the surface of Mars
is 3.7 Newtons per kilogram, the magnitude of the
normal force acting on the vehicle is
a) 320 N
c) 4400 N
b) 930 N
d) 5800 N
Some Hints: First draw a FBD. Next draw a pseudo FBD where
you replace the two angled forces with their x & y component
forces. Next calculate the two x & y force components for each of
the two tensions. Next realize that the stoplight is at rest in
equilibrium, so what does this tell you about the net force? Now,
use Newton’s second law to calculate the mass, m. Remember that
though mass is not a vector, weight or mg is a vector. Which
direction does mg point?
48. The speed of an object dropped in air will continue
to increase without limit until it strikes the ground.
Explain why this statement is true or why it is
false. ____________________________________
_________________________________________
_________________________________________
49. An object has a mass of 4.0 kg and is pulled in
opposite directions with forces of 3.0 N & 5.0 N.
What is the object’s acceleration?
50. If a 2.0 kg cart is being pulled with a force of
8.0 N against a frictional force of 2.0 N, what is the
value of k of the surface? What is the
acceleration of the cart?
55. The reason the elephant and the feather would
have the same value for their accelerations in a
vacuum is because
a) as mass increases, the force of gravity acting
increases proportionally by the same amount
b) as mass increases, the force of gravity acting
decreases proportionally by the same amount
c) their accelerations are the same in a vacuum
only if their masses are identical.
56. If a father and young son are on a frictionless ice
pond with a rope between them and they both
pull on the ends of the rope, the amount of force
exerted by the father on the son will be . ?
a) greater than the force exerted by the son
b) less than the force exerted by the son
c) equal to the force exerted by the son
51. An object of mass 2.5 kg is sliding on a surface
with an applied force of 8.0 N acting on it. If the
force of friction acting is 6.5 N, what would be the
acceleration of the object?
52. For the problem above, what would be the object’s
acceleration if there were an additional force of
10.0 N, pushing on the object?
53. If an object has a mass of 5.0 kg and it is
accelerating at 3.0 m/s2, while someone is pushing
on it with a force of 19 N, what is the force of
friction acting on the object?
54. The force of air resistance acting on an elephant,
compared to the force of air resistance acting on a
feather is . .
a) greater for the elephant
b) greater for the feather
c) the same for both the elephant and feather.
57. If the father has a mass of 80 kg and the son has a
mass of 40 kg, how will their accelerations
compare?
a) The acceleration of the father will be twice as
great.
b) The acceleration of the son will be twice as
great.
c) They will both have the same acceleration
58. A 400 N girl standing on a dock exerts a force of
100 N on a 10,000 N sailboat as she pushes it away
from the dock. How much force does the dock
exert on the girl?
a) 25 N
b) 100 N
c) 400 N
d) 10,000 N
59. A carpenter hits a nail with a hammer. Compared
to the magnitude of the force the hammer exerts on
the nail, the magnitude of the force the nail exerts
on the hammer during contact is
a) less
b) greater
c) the same
60. A projectile launched at an angle of 45 above the
horizontal travels through the air. Compared to the
projectile’s theoretical path with no air friction, the
actual trajectory of the projectile with air friction is
a)
b)
c)
d)
lower and shorter
lower and longer
higher and shorter
higher and longer
61. A box is pushed toward the right across a
classroom floor. The force of friction on the box is
directed toward the
a) left
b) right
c) ceiling
d) floor
62. The magnitude of the frictional force acting
between two surfaces depends on how many
factors?
a) 1
c) 3
b) 2
d) 4
66. When a balloon filled with air is released through
the air, it will fly all over the place. If the action
force is the rubber balloon pushing on the
molecules of air in the balloon, then the reaction
force is . . .
a) The air molecules outside the balloon pushing
back on the rubber balloon.
b) The air molecules inside the balloon pushing
back on the balloon.
c) The rubber balloon pushing on the air
molecules outside the balloon.
67. When the force of air resistance acting on a
skydiver is equal to the skydiver’s weight, what
will be the motion of the skydiver?
a) He will stop moving and be at rest because
the net force is zero.
b) He will continue to move but with a constant
velocity.
c) He will continue to accelerate.
63. Earth’s mass is approximately 81 times the mass
of the Moon. If Earth exerts a gravitational force
of magnitude F on the Moon, the magnitude of
the gravitational force of the Moon on Earth is
a) F
c) 9 F
b) F/81
d) 81 F
64. An 85 kg skydiver is accelerating through the air,
with a force of air resistance of 250 N acting on the
skydiver. First draw a free body diagram for the
skydiver. What is the acceleration of the
skydiver?
d) He will start moving upward, away
from the ground.
68. Consider a horse pulling a carriage along the
road by exerting a force on the carriage.
a) The reaction force acting on the horse cancels
the action force by the horse.
b) The reaction force acting on the horse is
opposite in direction but not equal
in magnitude to the action force by the horse.
c) The reaction force is acting on the same object
as the action force.
d) The reaction force is acting on a different
object and is equal in magnitude to the action
force.
65. Another skydiver of mass 70 kg, is moving
through the air with an acceleration of 5.0 m/s2
What is the force of air resistance acting on
her as she falls?
69. The force that a bug exerts on the windshield of
a moving car, compared to the force that the
windshield exerts on the bug is?
a) much greater
m2
b) much less
c) exactly equal
m1
(Textbook question #10)
70. A heavy mass is attached to a string and hung
from a horizontal bar and then a second string is
attached to the lower end of the mass. If you
want the bottom string to break when you pull
on it, should you pull the bottom string
Two masses are hanging over an Atwood pulley.
One has a mass of 235.0 grams (0.235 kg) and the
other mass has a mass of 238.0 grams (0.238 kg).
72. What is the net force (in N) causing the
system of masses to accelerate?
73. What is the acceleration of the two masses
using Newton’s Second Law?
74. If the masses moved a distance of 85.0 cm in
an average time of 4.7 seconds, what would the
acceleration of the two masses be using the
formula d = ½ at2?
a) slowly
b) with a sudden jerk
75. What is the tension in the string holding mass 1?
71. When a sealed flask filled with water has a metal
washer hanging from the cork, and you accelerate
the flask to the right, you would expect the washer
to “lag” behind and seem to be going left, due to
the inertia of the washer compared to an equal
volume of the water being less massive. When a
cork (of lesser density than water) replaces the
76. A spring scale is suspended horizontally between
two equal weights of 10 Newtons, each hanging
over a pulley and hanging downward over the two
ends of the table.
metal washer and the flask is quickly accelerated to
the right, while the flask is upside down, the
motion of the cork should be
10
a) to the right, also
b) to the left
10
Would the spring scale read 0, 10, or 20 Newtons,
or something else?
Approximate Coefficients of Friction
Surfaces
Kinetic (k)
Static (s)
Rubber on dry
concrete
Rubber on wet
concrete
Rubber on dry
asphalt
Rubber on wet
asphalt
Rubber on ice
0.68
0.90
Waxed ski on
snow
Wood on wood
0.05
0.14
0.30
0.42
Steel on steel
0.57
0.74
Copper on steel
0.36
0.53
Teflon on Teflon
0.04
Acceleration = 10 m/s2
0.58
0.67
79. The diagram below shows a 4.0 kg object
accelerating at 10 meters per second squared on a
rough horizontal surface.
0.85
0.53
Frictional
Force = Ff
m = 4.0 kg
Applied
Force = 50 N
0.15
What is the magnitude of the frictional force Ff
acting on the object?
a) 5.0 N
b) 10 N
c) 20 N
d) 40 N
These values can be used for the following
problems
77. A car’s performance is tested on various horizontal
road surfaces. The brakes are applied, causing the
rubber tires of the car to slide along the road
without rolling. The tires encounter the greatest
force of friction to stop the car on
a)
b)
c)
d)
dry concrete
dry asphalt
wet concrete
wet asphalt
78. The diagram below shows a block sliding down a
plane inclined at angle  with the horizontal.

/ // / / / / / / / / / / / / / / / / / / / / / / / / / / / / / /
As angle  is increased, the coefficient of kinetic
friction between the bottom surface of the block
and the surface of the incline will
a) decrease
b) increase
c) remain the same
80. An ice skater applies a horizontal force to a 20
kilogram block on frictionless, level ice, causing
the block to accelerate uniformly at 1.4 m/s2 to the
right. After the skater stops pushing the block, it
slides onto a region of ice that is covered by a thin
layer of sand. The coefficient of kinetic friction
between the block and the sand covered ice is 0.28
Calculate the magnitude of the force applied to the
block by the skater.
81. Referring to the previous problem, determine the
magnitude of the normal force acting on the block.
82. Again referring to the previous ice skater problem,
calculate the magnitude of the force of friction
acting on the block as it slides over the sand
covered ice.
83. A horizontal force of 8.0 N is used to pull a 20 N
wooden box moving toward the right along a
horizontal, wood surface as shown. (wood on wood)
20. N
wooden box
F = 8.0 N
87. A 10 kg wooden box sits on a wooden
surface. The coefficient of static friction
between the two surfaces is 0.42 A
horizontal force of 20 N is applied to the box.
What is the force of friction on the box?
(Remember how the force of static friction
compares to the force of kinetic friction)
(A) Calculate the magnitude of the frictional force
acting on the box.
(B) Determine the magnitude of the net force
acting on the box.
(C) Determine the mass of the box.
(D) Calculate the magnitude of the acceleration of
the box.
84. Compared to the force needed to start sliding a
crate across a rough level floor, the force needed to
keep it sliding once it is moving is
a) less
b) greater
c) the same
85. An airplane is moving with a constant velocity in
level flight. Compare the magnitude of the
forward force provided by the thrust of the engines
to the magnitude of the backward frictional
drag force.
86. When a 12 N horizontal force is applied to a
box on a horizontal tabletop, the box remains
at rest. The force of static friction acting on
the box is
a)
b)
c)
d)
88. Suzie pulls the handle of a 20 kg sled across
the yard with a force of 100 N at an angle of
30  above the horizontal. The yard exerts a
frictional force of 25 N on the sled.
(A) Find the coefficient of friction between
the sled and the yard.
(B) Determine the distance the sled travels if
it starts from rest and Suzie maintains her
100 N force for five seconds.
Air Resistance and Terminal Velocity
When an object falls through the atmosphere, it
accelerates until it reaches its maximum vertical
velocity, known as its terminal velocity (vt). Once
an object reaches terminal velocity, it continues
to fall at constant velocity with no acceleration.
In this situation, the force of gravity on the object
balances the drag force on the object. With zero
net force, the object is in equilibrium, and
continues to fall at a constant velocity as indicated
by Newton’s 1st Law of Motion.
The acceleration vs. time, velocity vs. time and
displacement vs. time graphs for an object falling
through the air would look as follows:
a (t)
g
Acceleration begins at g and over
time reduces to zero at terminal
velocity.
0N
between 0 N and 12 N
12 N
> 12 N
t
v (t)
terminal velocity
90. Lizzie stands on a scale in an elevator. If
the scale on the elevator floor reads 600 N
when Lizzie is riding upward at a constant 4
m/s, what is the reading on the scale when
the elevator is at rest?
a) 420 N
Velocity begins at 0 and
increases until reaching
terminal velocity.
b) 600 N
c) 780 N
t
y (t)
d) 840 N
Ramp Problems
91. Three forces act on a box on an inclined
plane as shown in the diagram below:
(Vectors not drawn to scale)
Displacement begins at 0 and
increases as speed increases,
until reaching a constant rate of
increase when velocity levels out
at v.
Normal Force
Friction
t
ELEVATORS
Note that a scale does not directly read the
weight of the person standing on it. Rather, the
scale provides a measure of the normal force the
scale exerts on the person. Realizing this makes
solving elevator problems an exercise in
applying Newton’s Laws of Motion.
89. A man with mass m stands on a scale in an
elevator. If the scale reading is equal to mg
when the elevator is at rest, what is the scale
reading when the elevator is accelerating
downward with a magnitude of a?
Weight
If the box is at rest, the net force acting on it
is equal to
a) the weight
b) the normal force
c) friction
d) zero
92. A 5 kg mass is held at rest on a frictionless
30  incline by force F. What is the
magnitude of F?
F
5 kg
a) m (g − ay)
b) m (g + ay)
c) m (ay− g)
30 
93. A 10 kg box slides down a frictionless 18 
ramp. Find the acceleration of the box, and the
time it takes the box to slide 2 meters down the
ramp.
96. The diagram represents a block at rest on an
incline. Which diagram best represents the forces
acting on the block? (Ff = frictional force, FN =
normal force, and Fw = weight.)
10 kg
block
18 
a)
FN
Ff
94. The diagram below shows a 1.0 x 105 N truck at
rest on a hill that makes an angle of 8.0 with the
horizontal.
Fw
FN
8.0
b)
Horizontal
Ff
What is the component of the truck’s weight
parallel to the hill?
a) 1.4 x 103 N
c) 1.4 x 104 N
b) 1.0 x 104 N
d) 9.9 x 104 N
Fw
c)
Ff
FN
Fw
95. A block weighing 10 N is on a ramp inclined at
30 to the horizontal. A 3 N force of friction, Ff,
acts on the block as it is pulled up the ramp at
constant velocity, with force, F, which is parallel to
the ramp, as shown in the diagram below. F
FN
d)
Ff
10 N
Ff
30
/////////////////////////////////// ///
Horizontal
(Vectors not drawn to scale)
What is the magnitude of force, F?
a) 3N
c) 10 N
b) 8 N
d) 13N
Fw
97. Which vector diagram best represents a cart
slowing down as it travels to the right on a
horizontal surface?
a)
98. Two masses, m1 and m2, are connected by a light
string over a mass-less pulley as shown.
Assuming a frictionless surface, find the
acceleration of m2.
FN
F1
F
m1
F mg
m2
b)
FN
F1
F
99. Situation: Tree falling toward the ground.
Identify an action/reaction pair of forces according
to Newton’s Third Law.
_________________________________________
_________________________________________
_________________________________________
_________________________________________
F mg
c)
FN
F1
d)
F
F mg
Identify one force acting on the tree.
_________________________________________
_________________________________________
_________________________________________
FN
100. Two masses are hung from a frictionless Atwood
pulley. If m1 is 5 kg and m2 is 7 kg, how far will
m2 fall in 2 seconds if released from rest?
F1
F
F mg
7 kg
5 kg
The Situation
Mr. Nicholls has asked for two volunteers from the
class to help with a demonstration. He has Frank and
Beth sit opposite each other on two chairs with wheels.
Beth takes off her shoes and puts her feet against
Frank’s knees. Beth pushes off, and the two chairs
move in opposite directions. Beth is quite a bit smaller
than Frank, so her chair moves noticeably faster than
his.
“Which student, Frank or Beth, experiences the
greater force?”, Mr. Nicholls asked.
Do you have an answer to Mr. Nicholls’ question?
The Prediction
Here are some responses from three students:
Mary:
“Beth did the pushing and Frank was
just sitting there, so Beth must have
been pushing harder that Frank
because she was causing the
acceleration.”
Cathy:
“I agree with Mary. Besides, she was
moving faster than Frank. Her
acceleration was larger, so she must
have experienced the greater force.”
Daniel:
“I disagree. Frank didn’t accelerate
as much as Beth because he has a
greater mass. A greater mass
requires a greater force, so Frank
must have experienced a greater
force than Beth.”
Which student do you agree with? Or do you have a
different answer or explanation?
The Answer
“Wait a minute,” says John, “I think this is one of
Nicholls’ trick questions. The first law says forces
cause accelerations, which we saw for ourselves. And
the second law says force, mass and acceleration are all
related, which is what we have been talking about. But
what about the third law?”
“John is right,” says Mr. Nicholls. “All of your
arguments make a lot of sense, but in fact the two
forces are equal in magnitude and opposite in direction
because of Newton’s Third Law of Motion.”
So then what is wrong with each of the explanations
given by Mary, Cathy, and Daniel? How can we
reconcile their observations with Newton’s Third Law
of Motion?”