\(gradient = \frac{change~in~y}{change~in~x} = \frac{change~in~distance}{change~in~time} = \frac{change~in~metres}{change~in~seconds} = m/s.\) The gradient of a distance-time graph represents speed.

Velocity-time graphs show how the velocity (or speed) of a moving object changes with time. These graphs also show if the object is moving at a constant speed or accelerating, decelerating, or still.