Suppose a question states:

> 
> A ball is dropped from a height of 2m. Find the time it takes for which the ball is in free fall.
> 
> 
> 

To solve this, we would plug in our known values into the kinematic equations.

But if the distance between the ball and the ground is 2m, then as soon as the ball travels 2m, at that exact moment it will touch the ground. So it will experience some deceleration at the 2m mark and thus, its acceleration will not be constant.

But to use kinematic equations, we must have constant acceleration motion. So why is using 2m as our displacement in the kinematic equations still correct? Shouldn't we instead use a distance that is JUST above the ground?