speed (physics)

Rate at which an object moves, or how fast an object moves. The average speed v of an object may be calculated by dividing the distance s it has travelled by the time t taken to do so, and may be expressed as:

v = s/t

The usual units of speed are metres per second or kilometres per hour.

Speed is a scalar quantity in which direction of motion is unimportant (unlike the vector quantity velocity, in which both magnitude and direction must be taken into consideration). Movement can be described by using motion graphs. Plotting distance against time in a distance–time graph allows the total distance covered to be worked out. See also speed–time graph.