# acceleration

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acceleration
/ak sel'euh ray"sheuhn/, n.
1. the act of accelerating; increase of speed or velocity.
2. a change in velocity.
3. Mech. the time rate of change of velocity with respect to magnitude or direction; the derivative of velocity with respect to time.
[1525-35; < L acceleration- (s. of acceleratio). See ACCELERATE, -ION]

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Rate of change of velocity.

Acceleration, like velocity, is a vector quantity: it has both magnitude and direction. The velocity of an object moving on a straight path can change in magnitude only, so its acceleration is the rate of change of its speed. On a curved path, the velocity may or may not change in magnitude, but it will always change in direction, which means that the acceleration of an object moving on a curved path can never be zero. If velocity is stated in metres per second (m/s) and the time interval in seconds (s), then the units of acceleration are metres per second per second (m/s/s, or m/s2). See also centripetal acceleration.

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rate at which velocity changes with time, in terms of both speed and direction. A point or an object moving in a straight line is accelerated if it speeds up or slows down. Motion on a circle is accelerated even if the speed is constant, because the direction is continually changing. For all other kinds of motion, both effects contribute to the acceleration.

Because acceleration has both a magnitude and a direction, it is a vector quantity. velocity is also a vector quantity. Acceleration is defined as the change in the velocity vector in a time interval, divided by the time interval. Instantaneous acceleration (at a precise moment and location) is given by the limit of the ratio of the change in velocity during a given time interval to the time interval as the time interval goes to zero (see analysis: Instantaneous rates of change (analysis)). For example, if velocity is expressed in metres per second, acceleration will be expressed in metres per second per second.

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Universalium. 2010.

Synonyms:

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