1. Motion & Speed
Ch. 3

2. Motion & Speed What is motion? 1. Changing one’s position
2. Moving from one place to another
3. You need a reference point to know if a position has changed.

3. Motion & Speed Example:
You look out the window and the mail truck is parked by the mailbox.
One minute later you see it down the block.
Even though you didn’t see the motion you know it moved because it’s position relative to the mailbox has changed.

4. Motion & Speed Example:
The earth’s crust is constantly in motion, but you can’t see it move.
We know it moves because it’s position changes relative to our point of reference – the sun.

5. Motion & Speed Changing Motion
1. Speed – the distance you are going divided by the time.
S =

6. D S T Motion & Speed Distance Speed Time (miles, km, m)
unit of distance
unit of time
Time
m/s, km/hr
(s, min, hr)

7. Motion & Speed Example:
A car is traveling at a speed of 100 m/s. How far will it get in 35 seconds?

8. Motion & Speed 2. Average speed – total distance / total time
-Used when speed varies

9. Motion & Speed Example:
You set out to ride your bike. You start at 0 km/hr and increase to 20 km/hr.
You then slow to 12 km/hr and come to a stop at a red light.
The light changes and you speed up to 35 km/hr.
It took you a total of 15 minutes to ride your bike a total distance of 5 km.
What is your average speed?

10. Motion & Speed
Example:

11. Motion & Speed
3. Instantaneous speed – your rate of motion at any time
-Speed shown by your speedometer