Acceleration is defined as the rate of change of velocity with respect to time.
If is the velocity and is the time then instantaneous acceleration is given as .
If is the initial velocity and is the final velocity is a total time period , then the average acceleration is given as .
Therefore, the unit of acceleration is .
Since velocity is a vector quantity, acceleration is also a vector quantity.
The product of acceleration undergone by the body and its mass gives the value of force applied by the body.
If is the displacement of the body, the acceleration can also be expressed as, .
Examples of Acceleration
For a body in a uniform circular motion, even though its speed remains constant, its direction is constantly changing. This causes a constant change in velocity that results in the generation of acceleration.
For a body that starts to move, it increases its velocity from , since it is initially at rest to a final velocity . Hence it undergoes acceleration.
Similarly, for a moving body that comes to rest, it decreases its velocity from to . Hence it undergoes a negative acceleration, retardation, or deceleration.
A freely falling body is acted upon by acceleration that occurs due to the gravitation attractive force of the earth.