## ::Velocity

### ::concepts

**Velocity**::object Speed::vector Constant::average ''t''::motion Moving::physics **Velocity**::change

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The **velocity** of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of its speed and direction of motion, e.g. {{safesubst:#invoke:val|main}} to the north. Velocity is an important concept in kinematics, the branch of classical mechanics that describes the motion of bodies.

Velocity is a physical vector quantity; both magnitude and direction are needed to define it. The scalar absolute value (magnitude) of velocity is called "speed", a quantity that is measured in metres per second (m/s or m⋅s^{−1}) in the SI (metric) system. For example, "5 metres per second" is a scalar (not a vector), whereas "5 metres per second east" is a vector.

If there is a change in speed, direction, or both, then the object has a changing velocity and is said to be undergoing an *acceleration*.

**Velocity sections**

Intro Constant velocity vs acceleration Distinction between speed and velocity Equation of motion Relative velocity See also Notes References External links

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