Download CH. 2 forces sample test

CH. 2 forces sample test
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____
____
____
____
____
____
____
____
____
1. Which of the following is an example of exerting a force?
a. a child running through a field
b. a train speeding down a track
c. a carpenter hammering a nail
d. an airplane soaring through the sky
2. What happens when two forces act in the same direction?
a. They cancel each other out.
b. The stronger one prevails.
c. They add together.
d. Their sum divided by two is the total force.
3. The tendency of an object to resist change in its motion is known as
a. mass.
b. inertia.
c. force.
d. balance.
4. The greater the mass of an object,
a. the easier the object starts moving.
b. the greater its inertia.
c. the more balanced it is.
d. the more space it takes up.
5. The force of gravity on a person or object on the surface of a planet is called
a. mass.
b. terminal velocity.
c. weight.
d. free fall.
6. One way to increase acceleration is by
a. increasing mass.
b. decreasing mass.
c. decreasing force.
d. increasing both force and mass proportionally.
7. The force that one surface exerts on another when the two rub against each other is called
a. friction.
b. acceleration.
c. inertia.
d. gravity.
8. Which of the following is an example of rolling friction?
a. your shoes on a sidewalk as you walk
b. bike tires on the road as you ride
c. a boat on the water as it sails
d. two hands rubbing together
9. When the only force acting on a falling object is gravity, the object is said to be
a. stationary.
b. decelerating.
____ 10.
____ 11.
____ 12.
____ 13.
____ 14.
____ 15.
____ 16.
____ 17.
____ 18.
____ 19.
c. in free fall.
d. a projectile.
Air resistance is a type of
a. motion.
b. acceleration.
c. velocity.
d. friction.
The force of gravity on a person or object at the surface of a planet is known as
a. mass.
b. inertia.
c. air resistance.
d. weight.
The law of universal gravitation states that any two objects in the universe, without exception,
a. attract each other.
b. repel each other.
c. combine to provide a balanced force.
d. create friction.
Forces can be added together only if they are
a. acting on the same object.
b. balanced forces.
c. unaffected by gravity.
d. substantial.
The product of an object’s mass and velocity is called its
a. inertia.
b. momentum.
c. acceleration.
d. force.
According to the law of conservation of momentum, when two objects collide in the absence of friction,
a. velocity decreases.
b. velocity increases.
c. momentum is not lost.
d. only the object with the larger mass continues on.
The achievement of lifting a rocket off the ground and into space can be explained by
a. Newton’s first law.
b. Newton’s second law.
c. Newton’s third law.
d. the law of conservation of momentum.
What is required for a rocket to lift off into space?
a. thrust that is greater than Earth’s gravity
b. mass that is greater than Earth’s
c. very little air resistance
d. more velocity than friction
An object that travels around another object in space is called a(n)
a. projectile.
b. inertia.
c. mass.
d. satellite.
Any force that causes an object to move in a circle is called a(n)
a. balanced force.
____ 20.
____ 21.
____ 22.
____ 23.
____ 24.
____ 25.
____ 26.
____ 27.
____ 28.
____ 29.
b. unbalanced force.
c. gravitational force.
d. centripetal force.
In physical science, a push or a pull is called a(n)
a. force.
b. acceleration.
c. inertia.
d. motion.
The momentum of an object is in the same direction as its
a. force.
b. acceleration.
c. velocity.
d. inertia.
How can you increase the momentum of an object?
a. by decreasing its velocity
b. by increasing its mass
c. by increasing its friction
d. by decreasing its acceleration
The amount of matter in an object is called its
a. inertia.
b. mass.
c. force.
d. balance.
Which of the following is an example of increasing friction intentionally?
a. waxing skis
b. adding grease to gears on a bike
c. throwing sand on an icy driveway
d. oiling a squeaky door
The force that pulls falling objects toward Earth is called
a. gravity.
b. free fall.
c. acceleration.
d. air resistance.
Objects falling through air experience a type of friction called
a. terminal velocity.
b. air resistance.
c. inertia.
d. rolling friction.
According to Newton’s third law of motion, when a hammer strikes and exerts force on a nail, the nail
a. creates a friction with the hammer.
b. disappears into the wood.
c. exerts an equal force back on the hammer.
d. moves at a constant speed.
The SI unit for force is the
a. newton.
b. meter.
c. kilogram.
d. pound.
Balanced forces acting on an object
a. always change the object’s motion.
b. sometimes change the object’s motion.
c. never change the object’s motion.
d. are not related to motion.
____ 30. The total momentum of a group of objects is conserved unless
a. outside forces do not act on the objects.
b. outside forces act on the objects.
c. the objects are moving.
d. there are more than two objects.
Modified True/False
Indicate whether the sentence or statement is true or false. If false, change the identified word or phrase to make the
sentence or statement true.
____ 31. Unbalanced forces do not change an object’s motion. _________________________
____ 32. The property of matter that resists a change in motion is called inertia. _________________________
____ 33. According to Newton’s second law of motion, weight depends on an object’s mass and the net force acting on
the object._________________________
____ 34. Friction depends on the types of surfaces involved and how hard the surfaces push together.
_________________________
____ 35. Mass and air resistance affect the gravitational attraction between objects. _________________________
____ 36. When the only force acting on a falling object is air resistance, the object is said to be in free fall.
_________________________
____ 37. Newton’s third law of motion states that for every action there is an equal but opposite unbalanced force.
_________________________
____ 38. A unit of momentum is kg•m/s. _________________________
____ 39. A rocket will move upward as long as the thrust is greater than the force of gravity.
_________________________
____ 40. The force that keeps a satellite in Earth orbit is always directed away from the center of Earth.
_________________________
Completion
Complete each sentence or statement.
41. The overall force on an object after all the forces are added together is called the ____________________
force.
42. Unbalanced forces acting on an object produce a change in the object’s ____________________.
43. A measure of an object’s ____________________ is a measure of the object’s inertia.
44. One ____________________ is the force required to accelerate 1 kilogram of mass at 1 meter per second per
second.
45. A person traveling in a car that stops suddenly keeps moving forward due to ____________________.
46. Wet pavement is more slippery than dry pavement because the force needed to overcome
____________________ friction is less than the force needed to overcome sliding friction.
47. The downward force acting on an object in free fall is the force of ____________________.
48. A(n) ____________________ is an object that is thrown.
49. When ____________________ equals the force of gravity on a falling object, the object reaches terminal
velocity.
50. The metric unit that is most often used to describe weight is the ____________________.
51. The force of gravity between you and Earth is greater than the force of gravity between you and a car because
Earth has more ____________________ than the car.
52. As the distance between two objects decreases, the gravitational force between them
____________________.
53. According to Newton’s third law of motion, the strength of a reaction force is ____________________ the
strength of the action force.
54. If the action force of a bat striking a ball accelerates the ball in one direction, the reaction force accelerates the
bat in the ____________________ direction.
55. The momentum of an object is in the same ____________________ as its velocity.
56. The momentum of a roller skater is not conserved because ____________________ acts on the skates.
57. During lift-off, the thrust on a rocket is directed ____________________.
58. Because the moon travels around Earth, it is a(n) ____________________.
59. The force of gravity is responsible for continuously changing the ____________________ in which a satellite
moves.
60. Friction acts in a direction ____________________ to an object’s direction of motion.
Short Answer
Use the diagram to answer each question.
61. What does the head of each arrow indicate?
62. What does the length of each arrow represent?
63. In what direction is the net force acting on the 1-kg object?
64. In what direction must a force be applied so that the forces on the 1-kg object are balanced?
65. Compare the acceleration of the 1-kg object with that of the 2-kg object.
66. Suppose a third force is applied to the 1-kg object in an upward direction. How will the object’s acceleration
change?
Use the diagram to answer each question.
Assume that all of the objects in the diagram are solid and made of the same material.
67. Compare the size and direction of the gravitational force exerted by each object in pair 1 of Set A.
68. In Set A, is the gravitational force greater between the objects in pair 1 or pair 2? Explain why.
69. In Set A, what would you have to do to the objects to make the gravitational forces between the objects in pair
2 the same as the forces between the objects in pair 1?
70. In Set B, explain the difference in the magnitudes of the gravitational forces between the two pairs of objects.
71. In Set C, explain the difference in the magnitudes of the gravitational forces between the two pairs of objects.
72. Can you identify a pair of balanced forces in the diagram? Explain your answer.
Essay
73. In an amusement park ride, a girl stands with her back against the inside wall of a circular room. The room
begins to whirl around. After the room reaches a constant speed, the floor drops down, but she doesn’t fall.
Identify three forces acting on her and give the direction of each. Explain which forces are balanced forces.
74. A book is sitting on the dashboard of a car that is stopped at a traffic light. As the car starts to move forward,
the book slides backward off the dashboard. Use the term inertia to explain what happened.
75. A block of wood is at rest on a wooden ramp. When wheels are attached to the block of wood, it moves down
the ramp. Explain each situation in terms of friction.
76. Compare the effects of gravity and air resistance on a falling skydiver before and after she opens her
parachute.
77. What is the law of conservation of momentum? How can you show that the law is true for two objects that
collide?
78. Why don’t action-reaction forces cancel out?
79. An object launched from Earth must attain a speed of 7,900 m/s to achieve a low orbit. What happens if the
object’s maximum speed is less than 7,900 m/s?
80. A skydiver with a mass of 70 kg accelerates to Earth at a rate of 9.8 m/s2 due to gravity. What is the force on
the skydiver? Explain how you determined the answer and its units.
CH. 2 forces sample test
Answer Section
MULTIPLE CHOICE
1. ANS:
STO:
2. ANS:
STO:
3. ANS:
STO:
4. ANS:
STO:
5. ANS:
STO:
6. ANS:
STO:
7. ANS:
STO:
8. ANS:
STO:
9. ANS:
STO:
10. ANS:
STO:
11. ANS:
STO:
12. ANS:
STO:
13. ANS:
STO:
14. ANS:
STO:
15. ANS:
STO:
16. ANS:
STO:
17. ANS:
STO:
18. ANS:
STO:
19. ANS:
STO:
20. ANS:
STO:
21. ANS:
STO:
22. ANS:
C
DIF: L3
5.1.C.1, 5.7.A.2
C
DIF: L2
5.7.A.2, 5.2.A.3
B
DIF: L1
5.7.A.2, 5.1.B.3
B
DIF: L2
5.7.A.2, 5.1.B.3
C
DIF: L1
5.7.A.2, 5.3.B.1
B
DIF: L2
5.7.A.2
A
DIF: L1
5.7.A.2
B
DIF: L2
5.7.A.2, 5.1.B.3, 5.1.B.2
C
DIF: L2
5.7.A.2, 5.7.A.1, 5.3.D.1.a
D
DIF: L2
5.7.A.2, 5.7.A.1
D
DIF: L1
5.7.A.2, 5.3.B.1
A
DIF: L1
5.7.A.2
A
DIF: L3
5.7.A.2, 5.2.A.3
B
DIF: L1
5.7.A.1, 5.3.B.1
C
DIF: L2
5.7.A.1, 5.1.B.1, 5.1.B.3
C
DIF: L2
5.7.A.1, 5.7.A.2, 5.8.D.2
A
DIF: L2
5.7.A.1, 5.7.A.2, 5.8.D.2
D
DIF: L1
5.7.A.1, 5.7.A.2, 5.8.D.2
D
DIF: L1
5.7.A.1, 5.7.A.2, 5.8.D.2
A
DIF: L1
5.1.C.1, 5.7.A.2
C
DIF: L3
5.7.A.1, 5.3.B.1
B
DIF: L3
REF: p. M-36
OBJ: M.2.1.1
REF: p. M-37
OBJ: M.2.1.2
REF: p. M-52
OBJ: M.2.3.1
REF: p. M-52
OBJ: M.2.3.1
REF: p. M-47
OBJ: M.2.2.2
REF: p. M-54
OBJ: M.2.2.2
REF: p. M-43
OBJ: M.2.2.1
REF: p. M-44
OBJ: M.2.2.1
REF: p. M-48
OBJ: M.2.2.3
REF: p. M-49
OBJ: M.2.2.3
REF: p. M-47
OBJ: M.2.2.2
REF: p. M-46
OBJ: M.2.2.2
REF: p. M-37
OBJ: M.2.1.1
REF: p. M-58
OBJ: M.2.4.2
REF: p. M-59
OBJ: M.2.4.3
REF: p. M-65
OBJ: M.2.5.1
REF: p. M-65
OBJ: M.2.5.1
REF: p. M-65
OBJ: M.2.5.2
REF: p. M-65
OBJ: M.2.5.2
REF: p. M-36
OBJ: M.2.1.1
REF: p. M-58
OBJ: M.2.4.2
REF: p. M-59
OBJ: M.2.4.2
STO:
23. ANS:
STO:
24. ANS:
STO:
25. ANS:
STO:
26. ANS:
STO:
27. ANS:
OBJ:
28. ANS:
STO:
29. ANS:
STO:
30. ANS:
STO:
5.7.A.1, 5.1.B.1, 5.1.B.3
B
DIF: L1
REF: p. M-46
OBJ:
5.7.A.2
C
DIF: L3
REF: p. M-43
OBJ:
5.7.A.2
A
DIF: L1
REF: p. M-46
OBJ:
5.7.A.2
B
DIF: L1
REF: p. M-49
OBJ:
5.7.A.2, 5.7.A.1
C
DIF: L3
REF: p. M-55, p. M-56
M.2.4.1
STO: 5.1.B.3, 5.7.A.1, 5.7.A.2
A
DIF: L1
REF: p. M-37
OBJ:
5.7.A.2, 5.2.A.3
C
DIF: L1
REF: p. M-39
OBJ:
5.7.A.1, 5.7.A.2
B
DIF: L1
REF: p. M-59
OBJ:
5.7.A.1, 5.1.B.1, 5.1.B.3
M.2.2.2
M.2.2.1
M.2.2.2
M.2.2.3
M.1.1.1
M.2.1.2
M.2.4.3
MODIFIED TRUE/FALSE
31. ANS: F, Balanced
DIF:
32. ANS:
OBJ:
33. ANS:
L1
REF: p. M-39
OBJ: M.2.1.2
T
DIF: L2
M.2.3.1
STO: 5.7.A.2, 5.1.B.3
F, acceleration
STO: 5.7.A.1, 5.7.A.2
REF: p. M-52
DIF:
34. ANS:
OBJ:
35. ANS:
L1
T
M.2.2.1
F, distance
OBJ: M.2.3.2
DIF: L1
STO: 5.7.A.2, 5.3.B.1
REF: p. M-43
REF: p. M-53
STO: 5.7.A.2
DIF: L1
36. ANS: F, gravity
REF: p. M-46
OBJ: M.2.2.2
STO: 5.7.A.2
DIF: L1
37. ANS: F, reaction
REF: p. M-48
OBJ: M.2.2.3
STO: 5.7.A.2, 5.7.A.1, 5.3.D.1.a
DIF:
38. ANS:
OBJ:
39. ANS:
OBJ:
40. ANS:
REF: p. M-55
L1
T
M.2.4.2
T
M.2.5.1
F, toward
DIF: L3
COMPLETION
OBJ: M.2.4.1
DIF: L2
STO: 5.7.A.1, 5.3.B.1
DIF: L2
STO: 5.7.A.1, 5.7.A.2, 5.8.D.2
STO: 5.1.B.3, 5.7.A.1, 5.7.A.2
REF: p. M-58
REF: p. M-65
STO: 5.7.A.1, 5.7.A.2, 5.8.D.2
OBJ: M.2.5.2
REF: p. M-65
41. ANS: net
DIF: L2
42. ANS: motion
REF: p. M-37
OBJ: M.2.1.1
STO: 5.7.A.2, 5.2.A.3
DIF: L1
43. ANS: mass
REF: p. M-38
OBJ: M.2.1.2
STO: 5.7.A.1, 5.7.A.2
DIF: L3
44. ANS: newton
REF: p. M-52
OBJ: M.2.3.1
STO: 5.7.A.2, 5.1.B.3
DIF: L3
45. ANS: inertia
REF: p. M-53
OBJ: M.2.3.2
STO: 5.7.A.2, 5.3.B.1
DIF: L2
46. ANS: fluid
REF: p. M-52
OBJ: M.2.3.1
STO: 5.7.A.2, 5.1.B.3
DIF: L3
47. ANS: gravity
REF: p. M-44
OBJ: M.2.2.1
STO: 5.7.A.2, 5.1.B.3, 5.1.B.2
DIF: L2
48. ANS: projectile
REF: p. M-48
OBJ: M.2.2.3
STO: 5.7.A.2, 5.7.A.1, 5.3.D.1.a
DIF: L1
REF: p. M-50
49. ANS: air resistance
OBJ: M.2.2.3
STO: 5.7.A.1
DIF: L3
50. ANS: newton
REF: p. M-49
OBJ: M.2.2.3
STO: 5.7.A.2, 5.7.A.1
DIF: L3
51. ANS: mass
REF: p. M-47
OBJ: M.2.2.3
STO: 5.7.A.2, 5.3.B.1
DIF: L3
52. ANS: increases
REF: p. M-47
OBJ: M.2.2.2
STO: 5.7.A.2, 5.3.B.1
DIF: L3
53. ANS: equal to
REF: p. M-47
OBJ: M.2.2.2
STO: 5.7.A.2, 5.3.B.1
DIF: L2
54. ANS: opposite
REF: p. M-55
OBJ: M.2.4.1
STO: 5.1.B.3, 5.7.A.1, 5.7.A.2
DIF: L3
55. ANS: direction
REF: p. M-56
OBJ: M.2.4.1
STO: 5.7.A.1
DIF: L3
56. ANS: friction
REF: p. M-58
OBJ: M.2.4.2
STO: 5.7.A.1, 5.3.B.1
DIF: L3
REF: p. M-59
OBJ: M.2.4.3
STO: 5.7.A.1, 5.1.B.1, 5.1.B.3
57. ANS: upward
DIF: L2
58. ANS: satellite
REF: p. M-65
OBJ: M.2.5.1
STO: 5.7.A.1, 5.7.A.2, 5.8.D.2
DIF: L2
59. ANS: direction
REF: p. M-65
OBJ: M.2.5.2
STO: 5.7.A.1, 5.7.A.2, 5.8.D.2
DIF: L3
60. ANS: opposite
REF: p. M-65
OBJ: M.2.5.2
STO: 5.7.A.1, 5.7.A.2, 5.8.D.2
DIF: L2
REF: p. M-43
OBJ: M.2.2.1
STO: 5.7.A.2
SHORT ANSWER
61. ANS:
The head indicates the direction of the force.
DIF: L1
REF: p. M-37
OBJ: M.2.1.2
62. ANS:
The length represents the size, or magnitude, of the force.
STO: 5.7.A.2, 5.2.A.3
DIF: L1
63. ANS:
to the left
REF: p. M-37
OBJ: M.2.1.2
STO: 5.7.A.2, 5.2.A.3
DIF: L2
64. ANS:
to the right
REF: p. M-37
OBJ: M.2.1.2
STO: 5.7.A.2, 5.2.A.3
DIF: L2
REF: p. M-39
OBJ: M.2.1.2
STO: 5.7.A.1, 5.7.A.2
65. ANS:
The acceleration of the 1-kg object is twice the acceleration of the 2-kg object.
DIF: L3
REF: p. M-54
OBJ: M.2.3.2
66. ANS:
The object will accelerate upward and to the left.
STO: 5.7.A.2
DIF: L3
REF: p. M-54
OBJ: M.2.3.2
STO: 5.7.A.2
67. ANS:
The gravitational forces are equal in size but opposite in direction.
DIF: L2
REF: p. M-46
OBJ: M.2.2.2
STO: 5.7.A.2
68. ANS:
The gravitational force between the objects in pair 2 is greater because the objects have a greater mass than
those in pair 1.
DIF: L2
69. ANS:
REF: p. M-47
OBJ: M.2.2.2
STO: 5.7.A.2, 5.3.B.1
Either move the objects in pair 1 closer together or those in pair 2 farther apart.
DIF: L2
REF: p. M-47
OBJ: M.2.2.2
STO: 5.7.A.2, 5.3.B.1
70. ANS:
The gravitational forces between the objects in pair 1 are greater than the forces between the objects in pair 2
because the objects in pair 2 are farther apart.
DIF: L2
REF: p. M-47
OBJ: M.2.2.2
STO: 5.7.A.2, 5.3.B.1
71. ANS:
The gravitational forces between the objects in pair 2 are greater than the forces between the objects in pair 1
because the objects in pair 2 are closer together.
DIF: L3
REF: p. M-47
OBJ: M.2.2.2
STO: 5.7.A.2, 5.3.B.1
72. ANS:
No pair of forces in the diagram is an example of a pair of balanced forces because each force in the pair acts
on a different object. Balanced forces can act on only one object.
DIF: L3
REF: p. M-37
OBJ: M.2.1.1
STO: 5.7.A.2, 5.2.A.3
ESSAY
73. ANS:
The three forces are centripetal force (inward), gravity (downward), and friction (upward). Because the girl
does not move up or down, the forces that act upward and downward on her must be balanced. These two
forces are friction and weight.
DIF: L3
REF: p. M-39
OBJ: M.2.1.2
STO: 5.7.A.1, 5.7.A.2
74. ANS:
When the car was stopped at the traffic light, the dashboard (which is part of the car) and the book were both
at rest. As the car accelerated forward, the dashboard moved forward. But no force was exerted directly on the
book, so it remained at rest. Because of its inertia, the book did not move forward when the dashboard moved
forward. From the reference point of the car, the book appeared to move backward, and fell off the dashboard.
DIF: L3
REF: p. M-52
OBJ: M.2.3.1
STO: 5.7.A.2, 5.1.B.3
75. ANS:
Without wheels, the force of sliding friction balances the gravitational force pulling the block down the ramp.
There is no net force on the block, so it does not slide down the incline. When wheels are attached, the force
of rolling friction is much smaller than the force of sliding friction. The gravitational force pulling the block
down the ramp is now greater than the friction force between the block and the ramp. Therefore, there is a net
force on the block pulling the block down the ramp, so the block begins to move in the direction of this
unbalanced force.
DIF: L3
REF: p. M-44
OBJ: M.2.2.1
STO: 5.7.A.2, 5.1.B.3, 5.1.B.2
76. ANS:
There is no difference in the force of gravity on the skydiver before and after she opens her parachute. The
downward force on the skydiver equals her weight plus the weight of the parachute. The air resistance on the
falling skydiver with her parachute open is greater than without the parachute open because the larger surface
area of the open parachute has greater air resistance acting on it.
DIF: L3
REF: p. M-48, p. M-49
OBJ: M.2.2.2
STO: 5.7.A.2, 5.7.A.1, 5.3.D.1.a
77. ANS:
The law of conservation of momentum states that the total momentum of objects that interact does not
change. In other words, the total momentum before and after a collision between two objects is the same. You
can show that the law is true by calculating the momentum of each object before the collision and again after
the collision. The total momentum before the collision will equal the total momentum after the collision.
DIF: L3
REF: p. M-59, p. M-61
OBJ: M.2.4.3
STO: 5.7.A.1, 5.1.B.1, 5.1.B.3, 5.7.A.2
78. ANS:
Forces cancel out only if they are acting on the same object. Action and reaction forces act on different
objects. For example, when a person kicks a ball, the action force is on the ball but the reaction force is on the
person’s foot. Therefore, the forces cannot cancel.
DIF: L2
REF: p. M-57
OBJ: M.2.4.1
STO: 5.7.A.1
79. ANS:
The object will not have enough speed to escape Earth’s gravity. It will eventually fall back to Earth’s
surface.
DIF: L3
REF: p. M-66
OBJ: M.2.5.2
STO: 5.7.A.2, 5.8.D.2
80. ANS:
Force = Mass  Acceleration = 70 kg  9.8 m/s2 = 686 kg  m/s2 = 686 N
According to Newton’s second law of motion, force equals mass times acceleration. Therefore, if you know
both mass and acceleration, you can find the force. In this case, the mass of the person and the acceleration
due to gravity were known. Since 1 N = 1 kg  m/s2, the final unit is the newton.
DIF: L3
REF: p. M-53
OBJ: M.2.3.2
STO: 5.7.A.2, 5.3.B.1