Remember, acceleration is the same as gradient, and acceleration = velocity change ÷ time. Look at the graph. The acceleration of the vehicle in the first 10 seconds is: ...

But if you calculate the acceleration without the graph, you are explicitly stating that the y-intercept is zero---which it might not be. So there are some actual reasons for making a graph.

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. Key fact The ...