## ::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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