# Bouncing Ball Momentum

1. Oct 8, 2011

### Megzzy

1. The problem statement, all variables and given/known data
I am currently working on a lab that deals with a bouncing ball where I need to find the KE and impulse yet I have no mass given.

2. Relevant equations
PE=mgh
KE=1/2mv
p=mv

3. The attempt at a solution
I have calculated KE by first finding the PE in the middle of the bounce where they will be equal.
So half way from the highest point I calculated PE using PE=mgh. Then assumed KE was the exact same.

I am however confused as to how to calculate impulse since I have no mass, just a KE value.

2. Oct 8, 2011

### t.francis

well what ARE you given?

3. Oct 8, 2011

### Megzzy

The height of the first bounce was 0.799 m. Therefore half that distance is 0.3995 (Where KE and PE are equal). I then took this is used it in the PE equation. The mass of the ball is not changing however so I don't see that it's needed.
Therefore PE=mgh
PE=0.3995m x 9.8
PE=3.92
Therefore KE=3.92.

I don't know how to get impulse from this.

4. Oct 8, 2011

### t.francis

Ep isn't 3.92

if you take Ep=Ek at halfway point then:

mgh=(1/2)mv^2

therefore it is implied that

gh=(1/2)v^2

but it is not implied that Ep=gh....

I don't see what impulse you're looking for? If it's the impulse the ball has when it hits the ground it depends on how squishy the ball is.

5. Oct 8, 2011

### t.francis

If all you've been given is the height of the first bounce the question is not answerable.