Question

what do you mean by acceleration ?

Answer 1

In physics, acceleration is the rate of change of velocity of an object with respect to time. An object's acceleration is the net result of any and all forces acting on the object, as described by Newton's Second Law. The SI unit for acceleration is metre per second squared (m s−2)
When changing direction, we might call this "non-linear acceleration", which passengers might experience as a sideways force. If the speed of the car decreases, this is an acceleration in the opposite direction from the direction of the vehicle, sometimes called deceleration.Passengers may experience deceleration as a force lifting them forwards. Mathematically, there is no separate formula for deceleration: both are changes in velocity. Each of these accelerations (linear, non-linear, deceleration) might be felt by passengers until their velocity (speed and direction) matches that of the car.

Answer 2

the rate of change of velocity with the time is called the acceleration ..

the acceleration of a body is represented by `a`

acceleration is equal to change of velocity by time taken for change

s i unit of acceleration is metre per second square acceleration is a vector quantity .