Distance, speed and acceleration – WJECDistance-time graphs of motion

Distance-time graphs

Distance-time graphs show how the distance travelled by a moving object changes with time.

These graphs also show if the object is moving at a constant speed or accelerating, going back to the starting point, or stationary.

Constant speed is shown by a straight rising line. The gradient or the steepness of the graph can be used to work out the speed. A steep line means the vehicle is moving fast.

A line curving upwards means that the vehicle is accelerating. The vehicle is getting faster as the line is getting steeper.

A flat horizontal line means the vehicle is still, as the distance isn’t changing.

The speed of the vehicle following the green line for the first 3 seconds is speed = distance ÷ time = gradient = 6 m ÷ 3 s = 2 m/s.

The total distance travelled by the vehicle on the green line is 7 m.

The mean speed of the vehicle on the green line is, average speed = total distance ÷ total time = 7 m ÷ 10 s = 0.7 m/s.

The speed of the vehicle following the purple line for the first 2 seconds is speed = distance ÷ time = gradient = 10 m ÷ 2 s = 5 m/s.

Look at this distance-time graph and answer the following questions.