Question

A tennis ball is dropped onto the floor from a height of 4.0 ft. It rebounds to a height of 3.0 ft. If the ball was in contact with the floor for 0.010 s, what was the average acceleration during contact? 

Answer 1

Let u be the velocity upon reaching ground 

Let v be the velocity upon rebounding from ground

But v is in upward direction, u downward. So for sign convention let’s take upward positive