Exam Review
Theory – Answer Key
1. A scalar quantity is a quantity described fully by magnitude.
A vector quantity is a quantity described fully by both magnitude and direction.
2. Vectors are concurrent if they act on an object at the same time.
3. Vectors must be added head-to-tail.
4. When adding vectors, the order of addition is irrelevant.
5. The resultant vector is the sum of vectors.
6. As the angle between two vectors increases from 0o to 180o, the magnitude of the resultant
decreases.
7. X and Y must be perpendicular if the Pythagorean Theorem is used to calculate the
magnitude of their resultant.
8. a) distance - how far an object travels
displacement – change in position
b) speed – how fast an object is moving
velocity – rate of change of position
9. How far? 14.0 m
Displacement? 0 m
10. a) Yes. If the penguin’s velocity is changing then either its speed and/or its direction must
change.
b) No. If the penguin’s velocity is constant neither its speed nor its direction can change.
11. If an object’s average velocity is zero for some interval, its displacement must be zero
during that time interval.
12. Divide by 3.6.
13. The slope of a position-time graph represents velocity.
14. A horizontal line on a position-time graph represents an object at rest.
Exam Review
Theory – Answer Key
15. The area under the graph line on a position-time graph represents nothing!
16. A change in direction on a position-time graph is represented by a change in the sign of
the slope of the graph line. (+ to - or vice versa).
17. Increasing velocity on a position-time graph is represented by a curve.
18. The slope of a velocity-time graph represents acceleration.
19. The area under the graph line on a velocity-time graph represents displacement.
20. Constant velocity on a velocity-time graph is represented by a horizontal line.
21. On a velocity-time graph, increasing velocity at a constant rate is represented by a straight
line with a positive slope. (The graph must begin at the point (0, 0).)
22. A change in direction is shown on a velocity–time graph when the graph line crosses
the time axis. (The region above the axis represents one direction, the region below the
axis represents the opposite direction).
23. A free body diagram is used to show the forces acting on an object.
24. If an object is at rest, the first law of motion explains the object’s state of motion.
25. If an object is at rest, the sum of the forces acting on an object is zero.
26. Inertia is the tendency of an object not to change its motion.
27. Mass the is sole measure of an object’s inertia.
28. If an object is falling at terminal velocity (constant velocity as an object falls through air),
the first law of motion explains its motion.
29. True. If an object’s speed changes, then it is accelerating.
30. No. If an object’s acceleration is zero, it does not mean that its velocity is necessarily
zero. The object could be traveling at constant velocity.
31. An object will accelerate if the sum of the forces acting on the object is not zero.
32. An object free falls if the only force acting on it is gravity.
Exam Review
Theory – Answer Key
33. The second law of motion explains an object’s motion if it is free falling.
34. The magnitude of the net force is equal to the magnitude of the objects weight.
The direction of the net force is down.
35. Acceleration represents the rate of change of an object’s velocity.
36. Net force is the term used to represent the sum of the forces acting on an object.
37. If an object falls at constant velocity, the magnitude of the net force is zero.
38. Yes, a car can have a negative velocity and a positive acceleration at the same time.
(The car is slowing down if the car’s velocity and acceleration have opposite directions.)
39. Mass and acceleration are inversely proportional.
40. Acceleration and net force are directly proportional.
41. No. The direction of an object’s acceleration and its velocity are not always the same.
42. You are accelerating when you ride a merry-go-round. Although you are travelling
at constant speed, you are continually changing direction.
43. If an object is dropped, its velocity increases while its acceleration is constant,
a = -9.8 m/s2.
44. The variable g represents the magnitude of the acceleration due to gravity.
45. Gravity is a vector quantity.
46. Mass is the amount of matter and weight is the force of gravity on an object.
47. At its maximum height, an object’s velocity is zero and its acceleration is 9.8 m/s2, down.
48. A feather reaches terminal velocity first because its weight is less than the weight of an
elephant. Terminal velocity is the velocity an object reaches when the force of air resistance equals weight.
Exam Review
Theory – Answer Key
49. If an object is moving at constant velocity, its acceleration is zero.
50. A dropped rock and a rock thrown downwards will have the same acceleration because
the only force acting on each rock is gravity.
51. The three conditions for an action-reaction pair of forces:
The magnitude of the forces must be equal.
The forces must act in opposite directions.
The forces must act on different objects.
52. The notation does not represent an action-reaction pair of forces. The forces are acting
on the same object, B.
53. Friction is the force that opposes an object’s motion.
54. An object must be resting on or moving along a surface.
55. Static friction is the force that opposes the start of motion. Kinetic friction is the force
that opposes the motion of a moving object.
56. True. Momentum is a vector quantity.
57. Yes, a train and a bullet can have the same momentum. The product of a bullet’s mass and
velocity can equal the product of the train’s mass and velocity.
58. An object’s momentum changes when a net force acts on the object.
59. The impulse-momentum theorem states that impulse equals change in momentum.
J = Δp
or
FΔt = mΔv
or
FΔt = m(vf – vi)
60. An airbag increases time and decreases force.
61. Positive work is done on an object when force and displacement act in the same direction;
negative is done on an object when force and displacement act in opposite directions.
Exam Review
Theory – Answer Key
62. No work is done when:
- a force acts on an object, but the object does not move.
- the force acting on an object is perpendicular to its displacement.
- an object is displaced, but no force acts on the object (ie. an object moves at constant
velocity along a frictionless surface.
63. False. Work is not a vector quantity.
64. No, the amount of work done on an object is independent of the amount of time it
takes to do the work.
65. Power is the rate of doing work.
66. If an object has the ability to do work, it has energy.
67. Gravitational potential energy is the energy stored due to an object’s height above
a designated reference level. Kinetic energy is the energy due to an object’s motion.
68. If an object’s change in kinetic energy is negative, the object is slowing down.
69. False. Kinetic energy is directly proportional to the square of an object’s velocity.
70. An object’s gravitational potential energy will be negative if the object is located below
the designated reference level.
71. False. An object’s gravitational potential energy is dependent on its height not the
length of the path that is taken to reach its maximum height.
72. Yes, a baseball can have both kinetic energy and gravitational potential energy.
73. The work-energy theorem states that the work done on an object is equal to its change
in kinetic energy.
W = ΔKE
or
𝐹𝑑 =
1
2
𝑚(vf2 – vi2)
74. True. Energy is a scalar quantity.
75. Mechanical energy is the sum of potential energy and kinetic energy.
76. Energy cannot be gained or lost. The total energy does not change.