Homework Help: Bouncing Ball

1. The problem statement, all variables and given/known data

a rubber ball mass of 0.08 kg bounces vertically on a concrete floor. the ball strikes the floor at 10 ms-1 and rebounds at 8 ms-1. The time in contact with the floor is 0.05 sec.
Calculate the average net force acting on the ball during the contact with the floor.

2. Relevant equations
E=F/t

F=0.5mv^2

3. The attempt at a solution

(0.5x0.08x10^2)/0.05
= 80N

I get a force of 80 N but to me it seems to much to be true... Help???

 

So change in momentum= 1.44 kgms-1

F=1.44/0.05
=28.8N

that seems more plausible Thanks for the help!!!