Learn and revise motion in a straight line, acceleration and motion graphs with BBC Bitesize Combined Science AQA Synergy study guide.

If the velocity-time graph is curved, the acceleration can be found by calculating the gradient of a tangent to the curve.

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.