1. Velocity-time graphs

2. Edexcel Statements

3. Velocity-time graph What story does the graph tell?

4. Finding the acceleration velocity Time Change in velocity Change in time So the gradient of a velocity time graph gives the acceleration

5. The steeper the gradient the greater acceleration

6. What if the gradient is zero ? Velocity Time A horizontal line means that the object has a constant (or uniform) velocity.

7. What if the slope is negative? Velocity Time

8. Calculating the average velocity

9. Example 1 A car accelerates uniformly from rest for 10 seconds, to then travels at a constant velocity for 20s. Then the driver brakes hard and comes to a complete stop in 2s. Sketch the velocity – time graph Velocity (m/s) Time (s)

10. The area under a velocity-time graph gives the distance travelled Velocity (m/s) Time (s)

11. Example 2 Plot a velocity-time graph using the data given Velocity (m/s) 0.02.04.08.012.0 Time (s)0.01.02.03.04.05.06.07.08.0 Draw a line of best fit for each section and use the graph to find a)The acceleration in the first 2 seconds b)The acceleration between 2.0 and 3.0 seconds c)The total distance travelled d)The average speed for the 8 seconds

13. Summary The gradient of a velocity-time graph gives the acceleration. A steeper gradient means that the object is accelerating faster A zero gradient (a horizontal line) means the object is travelling at a constant velocity A linear graph/section shows that the acceleration is constant If any section of the graph is curved, then the acceleration is changing and is no longer constant.