We can find out the acceleration
of a body at any instant, it coincides with the average acceleration
between two very short instants.
If we discover the acceleration of a moving body between two very near
instants, we will find out the value of instantaneous
acceleration.
To be precise, instantaneous
acceleration is the derivative of the
velocity vector with respect to time, or what is the same thing: the
limit of the increase in velocity when time tends towards zero.
