In physics, velocity is defined as the rate of change of position. It is a vector physical quantity, both speed and direction are required to define it. In the SI (metric) system, it is measured in meters per second (m/s). The scalar absolute value (magnitude) of velocity is speed. For example, "5 metres per second" is a speed and not a vector, whereas "5 metres per second east" is a vector. The average velocity (v) of an object moving through a displacement ( Delta x) in a straight line during a time interval ( Delta t) is described by the formula:
