when the velocity of a particle changes with time, the particle is said to be accelerating.
– The Average acceleration of the particle is definded as the change in velocity divided by the time interval during which that change occurs:
– Instantaneous acceleration: it is useful to define it as the limit of the average acceleration as approaches zero.
the instantaneous acceleration equals the derivative of the velocity with respect to time
that is, in one-dimensional motion, the acceleration equals the second derivative of with respect to time.