# Acceleration ## Etymology

Latin acceleratus, past participle of accelerare, from ad- + celer swift

## Definitions

• 1 : to bring about at an earlier time <accelerate their departure>
• 2 : to cause to move faster <accelerated his steps>; also : to cause to undergo acceleration
• 3 a : to hasten the progress or development of <accelerate our efforts>
b : increase <accelerate food production>
• 4 a : to enable (a student) to complete a course in less than usual time
b : to speed up (as a course of study)
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## Description

In physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up. However, as a vector quantity, acceleration is also the rate at which direction changes. Acceleration has the dimensions L T −2. In SI units, acceleration is measured in meters per second squared (m/s2).

In common speech, the term acceleration commonly is used for an increase in speed (the magnitude of velocity); a decrease in speed is called deceleration. In physics, a change in the direction of velocity also is an acceleration: for rotary motion, the change in direction of velocity results in centripetal (toward the center) acceleration; where as the rate of change of speed is a tangential acceleration. In classical mechanics, for a body with constant mass, the acceleration of the body is proportional to the resultant (total) force acting on it (Newton's second law) where F is the resultant force acting on the body, m is the mass of the body, and a is its acceleration.