A tennis ball with a speed of 28 m/s is mov-
ing perpendicular to a wall. After striking
the wall, the ball rebounds in the opposite
direction with a speed of 19.516 m/s.
If the ball is in contact with the wall for
0.0101 s, what is the average acceleration of
the ball while it is in contact with the wall?
Take “toward the wall” to be the positive
direction.