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, acceleration is the rate at which something speeds up or slows down. However, as a vector quantity, acceleration is also the rate at which direction changes.
Acceleration has the dimensions L Tâˆ’2. In SI units, acceleration is measured in metres 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 motion on a planar surface, the change in direction of velocity results in centripetal acceleration; whereas the rate of change of speed is a tangential acceleration.