Example: Using the gradient or slope of a distance - time graph to work out the speed of an object Calculate the speed of the object represented by the green line in the graph below, from 0 to 3 s.

Therefore, we can say that the motion of a freely falling body is an example of a non-uniform motion. The distance-time graph of the non-uniform motion is a curved line.

From a straight-line graph the gradient can be calculated. The gradient of a distance-time graph is equal to the speed, and the gradient of a force-extension graph is equal to the spring constant.