Physics Unit Summary
Chapter 8
1. Terms Used to Describe Motion
• Distance is the length of the path between two points and position is the object’s location measured in relation to a reference point. Both quantities are measured in metres (m).
• Displacement is the straight line distance from one location to another as well as the direction. Displacement is calculated as the final position minus the initial position.
• The difference between the final time and the initial time is called the time interval and is measured in seconds (s).
• Speed is the distance an object travels divided by the time to travel that distance.
• Average velocity is the displacement of an object during a time interval divided by the time interval.
• The SI unit for speed and velocity is m/s, but both are commonly measured in km/h.
2. Scalars and Vectors
• Scalars have a magnitude only, whereas vectors have both a magnitude and a direction.
• Position, displacement, and average velocity are vector quantities.
• Distance, speed, and time interval are scalar quantities.
• Opposite directions are designated by opposite signs (positive + or negative –).
• The magnitude of the displacement will equal the distance if the object travels in one direction in a straight line.
3. Uniform Motion
• An object that travels equal displacements in equal time intervals is said to display uniform motion.
• Objects in uniform motion have a constant velocity. This means that they do not speed up or slow down or change their direction of motion.
• Uniform motion is represented as a straight line on a position-time graph.
4. Position-Time Graph
• A best-fit line is a smooth curve or straight line that most closely fits the general shape outlined by the plotted data points.
• The slope of the best-fit line on a position-time graph is the object’s average velocity.
• A negative slope and a positive slope on a position-time graph indicate that the object is moving in opposite directions.
• A zero slope on a position-time graph indicates that the object is not moving.
5. Calculating Average Velocity
• The relationship between average velocity, displacement, and time interval is given by the equation .
• The displacement can be calculated by:
• The time interval can be calculated by:
• A velocity in km/h can be converted to m/s by multiplying by 1000 and dividing by 3600.

Chapter 9
1. Describing Acceleration
• Acceleration is the rate of change in velocity.
• The direction of the acceleration is the same as the direction of the change in velocity.
• If an object’s acceleration is in the same direction as its velocity, the object’s speed will increase.
• If an object’s acceleration is in the opposite direction as its velocity, the object’s speed will decrease. This acceleration is sometimes called deceleration.
• Zero acceleration means the object’s velocity is constant.
2. Calculating Acceleration
• A change in velocity is calculated by subtracting the initial velocity from the final velocity.
• The SI unit for acceleration is m/s2.
• The relationship of acceleration, change in velocity, and time interval is given by .
• Both change in velocity and time interval can be calculated by rearranging the acceleration equation such that:  and .
3. Velocity-Time Graph
• The slope of a velocity-time graph is average acceleration.
• Constant acceleration is represented by a straight line on a velocity-time graph.
• A positive slope represents the object increasing its velocity in the direction indicated by the positive y-axis.
• A negative slope represents an acceleration opposite the direction indicated by the positive y-axis. This could represent the object slowing down if its initial velocity is in the positive direction or speeding up if its initial velocity is in the negative direction.
• A zero slope on a velocity-time graph means the object is moving with a constant velocity.
4. Acceleration Due to Gravity
• Air resistance acts against the direction of motion of an object.
• In the absence of air resistance, all objects accelerate at the same rate due to gravity.
• Absent air resistance, the acceleration due to gravity near the surface of Earth is 9.8 m/s2 downward.