1. The Nature of Forces and Motion.
SPS8. Students will determine relationships among force, mass, and motion.
a. Calculate velocity and acceleration.

2. Distance and Displacement:
Distance is a measure of “how far an object has moved” and is independent of direction.
Example: If a person travels 50m due east, turns and travels 10m due south, then turns and travels 50m due west the distance traveled is 110m
50 meters
10 meters
50 meters

3. Distance and Displacement:
Displacement refers to both the distance and direction of an object’s change in position from the starting point of origin.
Example: If a person travels 50m due west, turns and travels 10m due south, then turns and travels 50m due east the total displacement is 10m south.
50 meters
10 m
10 meters
50 meters

4. Speed
Speed is how fast something is going.
It is a measure of the distance covered divided by the unit of time it took to cover the distance.
Speed is calculated by dividing the Distance traveled by the Time it took to travel the Distance D
Speed is measured in meters per second ( m/s) S T

5. Types of speed
Instantaneous speed is “the speed at a specific instant”
A speedometer measures instantaneous speed. .
Average speed is “the total distance covered in a particular time period”

6. But What is Velocity? D V T

7. Velocity
Velocity can change even if the speed stays constant.
Example:
A racecar on a circular track moving at a constant speed of 100 km/hr has a constantly changing velocity because of a changing direction of travel

9. I seem to have forgotten something……?
Quiz time!!!!!
1) If you ride your bicycle down a straight road for 500 m then turn around and ride back, your distance is ____ your displacement.
(A) greater than
(B) less than
(C) Equal
(D) Can’t determine

10. Quiz time!!!!! 2) The speed you read on a speedometer is ____.
(A) instantaneous speed
(B) average speed
(C) constant speed
(D) velocity

11. Quiz time!!!!! 3) 3 m/s north is an example of a(n) ____.
a. speed c. position
b. velocity d. acceleration

12. Quiz time!!!!!
4) A merry-go-round horse moves at a constant speed but at a changing ____.
a. velocity c.inertia
b. balanced force d.unbalanced force

13. Quiz time!!!!!
5) A car travels at a speed of 50m/s for 20 seconds. What distance did it cover?
a. 2.5m c. 400m
b. 1000m d.0.4m

14. Distance time Graph
The slope of a graph showing distance plotted over time gives the velocity ( or speed).
Because Change in distance over time is velocity!
The steeper the line the greater the velocity

15. What Is Change in Velocity (or Speed) over a period of time called?
Acceleration!

16. Remember that the slope of a a distance - time graph gives the velocity ( or speed)

17. If we plot the velocity of an object over a period of time:

18. Acceleration

19. Because velocity involves both speed and direction, either a change in speed (slowing down or speeding up) or a change in direction causes acceleration.

20. Negative Acceleration ( Deceleration) is seen when an object is slowing down.
This means that its velocity is decreasing with time.

21. No Acceleration is seen when an object is neither speeding up nor slowing down
This means that its velocity is constant

22. Acceleration.

23. Acceleration = Change in velocity (m/s) (m/s2 ) Time (s)
But how do we calculate the “change in velocity”?
Change in velocity= Final velocity(Vf) – Initial velocity(Vi)

24. Quiz time!!!!! 6) Acceleration is rate of change of ____.
a. position c. velocity
b. time d. force

25. Quiz time!!!!!
7) A horizontal line on a velocity/time graph shows ____ acceleration.
a. positive c. changing
b. negative d. zero

26. Quiz time!!!!!
8)If you ride your bike up a hill, then ride down the other side, your acceleration is ____.
a) first positive, then negative
b) all negative
c)first negative, then positive
d) all positive