1. 8.1 The Language of Motion
Some common words used to describe motion include:
Distance
Time
Speed
Position
How would you describe the motion of the soccer ball before and after it is kicked?
What key words did you use when describing this situation?

2. Direction Makes a Difference
Two main types of quantities:
Scalars: Describe magnitude but not direction. (Magnitude is the size of a measurement)
Example: Johnny walked 25 km
Vectors: Describe magnitude and direction.
Example: Johnny walked 25 km North
Every time you use a map or give directions, you are using vectors.

3. Vectors vs. Scalars
You can always tell if a quantity is a vector because there will be an arrow drawn above it.
Example:
A scalar has no arrow.

4. Position and Reference Point
Position (d) is a vector that describes your location relative to a reference point.
Example: Johnny is 5 m from the teacher’s desk.
In this example, the teacher’s desk is a reference point, which we need to determine the position.

5. Describe the position (d) of the car using different reference points
Describe the position (d) of the car using different reference points. Note that you need to use direction in your description, so position is a vector.

6. Distance vs. Displacement
Distance (d) is a scalar that tells you how far something has travelled.
Example: Johnny ran a distance of 400 m
Displacement (∆d) is a vector that describes your position relative to where you started. It describes your change in position.
Example: Johnny ran 400 m North of his home.
We measure both distance and displacement in metres (m).

8. Example
A car leaves home and drives 10 km to the store and then returns home. The car has driven a total distance of 20 km but its final displacement is 0 km.

9. Time Interval ti = initial time
Time interval or change in time is calculated by:
Where: Δt = change in time (the Δ symbol is the greek letter delta. It means “change”.
ti = initial time
tf = final time

10. Example
The time interval to move from the fire hydrant to the sign is calculated by:

11. Displacement Displacement or change in position is calculated by:
Where: = change in position or displacement
= initial position
= final position

12. Displacement and Distance
Between 2 s and 5 s, the skateboarder’s:
displacement is 5 m [E] and
distance travelled is 5 m.

13. Watch for Signs Turn to page 349 for common sign conventions
Copy Figure 8.8 into notes
Turn to page 352 in textbook and do Activity 8-1B

15. Uniform Motion
Uniform motion is a term that describes objects that do not speed up, slow down, or change direction.
In other words, they travel at constant velocities (we will discuss velocity more later)

16. Example
The position of the ball in this photo is shown at equal time intervals. How would you determine if this motion is uniform motion?
What would the picture look like if the ball was NOT in uniform motion?

17. Graphing Uniform Motion
Motion of an object can be analyzed by drawing a position-time graph.
A position-time graph plots position data on the vertical axis (y-axis) and time data on the horizontal axis (x-axis).

18. Uniform motion is represented by a straight line on a position-time graph.

19. Positive Slope Slants up to the right.
Indicates an object travelling in the positive direction
(ie: North, East, to the right, up, etc.)

20. Zero Slope
Horizontal line.
Indicates that the object is stationary.

21. Negative Slope Slants down to the right.
Indicates an object travelling in the negative direction (ie: South, West, to the left, down, etc.)

22. Analyzing a Position-Time Graph
Turn to page 355 in textbook and do Activity 8-1D