In physics, velocity is 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) or ms−1. The scalar absolute value (magnitude) of velocity is speed. For example, "5 meters per second" is a scalar and not a vector, whereas "5 meters per second east" is a vector. The average velocity v of an object moving through a displacement (Δx) during a time interval (Δt) is described by the formula:
- Robert Resnick and Jearl Walker, Fundamentals of Physics, Wiley; ISBN 0471232319.