A graph that shows velocity plotted against time for a particle moving in a straight line. Let x(t) and v(t) be the displacement and velocity, respectively, of the particle at time t. The velocity–time graph is the graph y = v(t), where the t-axis is horizontal and the y-axis is vertical with the positive direction upwards.
The gradient of the velocity–time graph at any point is equal to the acceleration of the particle at that time. Also,
is the displacement of the particle during the time interval. Note that this is not necessarily the distance travelled.