Motion and Average Acceleration -Help-

[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?

 

[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 $$F=ma$$