1. Area under Graphs The area under a speed vs time graph gives you the distance the object travelled. Split the graph into shapes you can calculate the area of then add up the areas. Practice COPY

2. Acceleration and speed-time graphs

3. Using graphs slopeWe can use the slope of a distance – time graphs to find the speed of an object. straight.To do this the graph line must be straight. Copy

4. Handout

5. slope Calculate the slope for each Car The average speed of Car A = The average speed of Car B = The average speed of Car C =

6. Acceleration Think… what is acceleration? Share with your neighbour What did you think? (Hands up!)

7. Acceleration video

8. So acceleration is… The change in speed over time. It is how much the speed has increased (or decreased) in a particular amount of time. COPY

9. Acceleration, a; ms -2 Acceleration is a measure of how fast an object changes it’s speed. v av at Copy

10. Speed time graphs The gradient (slope) of a speed time graph give the acceleration of the object. If the line is flat, the speed isnt changing and acceleration= 0 The distance traveled is given by the area under the graph. COPY

11. So if we have a speed time graph… Between A and B, the speed is increasing with time. Therefore the object is accelerating.

12. So back to our graph… The slope is given by Rise/run. The rise is speed, and the run is time… The gradient = acceleration

13. Plot a speed – time graph using this data. Plot the two skiers on the same axes. Draw a staright line of best fit for both skiers (use a ruler). Speed (ms -1 ) time (s)

14. Use graph to calculate acceleration Time (s)Speed Skier 1 (ms -1 ) Speed Skier 2 (ms -1 ) 000 1510 2 20 31530 42040 52550 Copy

15. Calculate the slope of the two skiers. How quickly was skier 1 accelerating? How quickly was skier 2 accelerating?

16. So acceleration is… Acceleration = Speed/time