# Motion and Average Acceleration -Help-

1. Sep 7, 2005

### febreze

I've been killing myself over this problem because I cannot figure it out. Can someone please help me?

A tennis ball with a velocity of 40.0 m/s to the right is thrown perpendicularly at a wall. After striking the wall, the ball rebounds in the opposite direction with a velocity of -8 m/s to the left. If the ball is in contact with the wall for 0.014 s, what is the average acceleration of the ball while it is in contact with the wall?

2. Sep 7, 2005

### zwtipp05

Have you learned about momentum and impulse?

Force multipled by time gives you change in momentum.
$$F\Delta{t}=mv_f-mv_i$$

Then just use $$F=ma$$