Speed-time graphs show speed on the vertical axis and time on the horizontal axis. The gradient of a speed-time graph represents acceleration because:

gradient =

= metres per second per second.

Metres per second per second can be written as or .

A negative gradient shows the rate of 'slowing down' or deceleration.

Velocity-time graphs show velocity on the vertical axis. Acceleration is still represented by the gradient.

The gradient of speed-time and velocity-time graphs represent acceleration.

The area under a speed-time graph represents the distance travelled. Likewise, the area under a velocity-time graph represents the displacement of the moving object. If the velocity is always positive, then the displacement will be the same as the distance.

Describe what is happening in this journey.

Between 0 and 4 seconds:

- the object is accelerating at
- it travels

Between 4 and 7 seconds:

- the object is travelling at a constant velocity of 8 m/s
- it travels

Between 7 and 10 seconds:

- the object is accelerating at
- this means it is slowing down or decelerating at a rate of
- it travels