Speed is defined as the total distance traveled divided by the total time it took to travel that particular distance. Speed is a scalar quantity with dimensions distance/time. Speed is measured in the same physical units of measurement as velocity, but does not contain an element of direction. Speed is thus the magnitude component of velocity. Velocity contains both the magnitude and direction components. Example: For human beings, an average walking speed is about 3 mph (~5 km/h, 1.39m/s).