Velocity is the rate at which a point or particle changes its position. The change in the position of a particle must have both magnitude and direction, so that velocity is a vector quantity. It may vary both in regard to its magnitude and to its direction, and its magnitude may be constant while its direction continually varies, as when a train goes round a curve.
To measure a particle's velocity, two things must be determined ; (a) the space over which the particle has moved in a given time; (b) the change of direction of motion during this time. Hence, if a particle moves in a straight line and so preserves a constant direction, and passes over equal spaces in successive equal times, its linear velocity is said to be constant. If, however, it is moving in a circle, say, and passes over equal arcs in equal times, its speed is constant, but its linear velocity is not. Constant speed is measured by dividing the space passed over in any given time by that time. Unit speed is such that unit space is passed over in given time.
The unit of velocity is that velocity with which a point passes over unit length in unit time, e.g one foot per second or one meter per second. Angular velocity is angular speed round an axis. To define it fully, a straight line must be given in length, direction, and position, and is known as a rotor or localised vector. Research Velocity
Abbreviations
SciTech
Research Velocity