# Homework Help: Physics linear momentum/ average force

1. Sep 25, 2013

### astru025

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

A very hard rubber ball (m = 0.2 kg) is falling vertically at 3 m/s just before it bounces on the floor. The ball rebounds back at essentially the same speed. If the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

2. Relevant equations

Net force= change in momentum/ time taken
Linear momentum= mass x velocity

3. The attempt at a solution
I found the linear momentum of the ball before it hits the ground: .2 kg x 3 m/s= .6
After this I am lost and am not sure what I do next. I not sure what I need to do in order to find average force from this information.

2. Sep 25, 2013

### Abhilash H N

Now you have the initial momentum find the final momentum... Then apply the formula for average force...

3. Sep 25, 2013

### haruspex

... Bearing in mind that momentum is a vector, so if you are measuring momentum as positive downwards then after the bounce it will be negative.