Question

define acceleration?????????????

Answer 1

the simple definition for acceleration is the rate of change of velocity is known as acceleration


but if we define it clearly it is

then the rate of speed increases by time by time is known as acceleration and when it reduces it is known as deceleration

Answer 2

1. When an object is moving then it is in motion state. The change in motion is called its velocity and change is velocity is called acceleration. 
2.The acceleration formula is given as:

Acceleration (a) = change in velocityTime Taken
                       ⇒ a = v − u/t
So unit for acceleration is m/s2. It can also be interpreted using Newton’s second law i.e.
F = ma