1. Distance-time graphs

2. Edexcel Statement

3. Introduction Distance time graphs are a good way of describing motion. The distance (the dependent variable) is plotted on the y axis and the time (the independent variable) is on the x axis. Distance time graphs are useful because we can visualise the motion much more easily than with a table, and we can use them to calculate speed.

4. Distance-time graph of someone walking to a bus stop. What story does the graph tell?

5. Finding the speed Distance Time Change in distance Change in time So the gradient of a distance time graph gives the speed

6. The steeper the gradient the bigger the speed

7. What if the gradient is zero? Distance Time A horizontal line means that the object has stopped moving or is stationary.

8. What do you notice about the graphs? They are all linear. This means the object is not changing speed at any point. This is called uniform or constant speed

9. Summary The gradient of a distance-time graph gives the speed. A bigger gradient means that the object is going faster A zero gradient means the object is stationary A linear graph shows that the speed is constant

10. Charlie the Cheetah’s Day out Draw this distance-time grap h Charlie set off to see a friend. A. He travelled 80m in 4 seconds. B. He stopped to have a drink from a water hole for 60 seconds. C. He saw his friend in the distance so he walked towards him covering 200 m in 15 seconds. D. They sat and chatted for two minutes. E. Charlie got up suddenly saying he had left his oven on and raced back home in 10 seconds Luckily his cakes were fine.

11. Questions Calculate his speed at each point. What was his average speed?