# Tennis Ball rebounds

1. Feb 28, 2009

### julz3216

1. The problem statement, all variables and given/known data
A 60 tennis ball with an initial speed of 33 hits a wall and rebounds with the same speed. The figure (Intro 1 figure) shows the force of the wall on the ball during the collision. t=6
http://session.masteringphysics.com/problemAsset/1070440/4/09.EX11.jpg

What is the value of , the maximum value of the contact force during the collision?

2. Relevant equations

p=mv
change in p = F *change in time
F=ma

3. The attempt at a solution

I attempted and got Fmax = 1320

2. Mar 1, 2009

### LowlyPion

Not sure about your units, but I'll go with 60 g for a tennis ball and 33 m/s.

Impulse is Δmv.

But your force varies during the time. So you want to take the integral of the area under the F - t graph they provide. Each square is an Fmax * 1ms. When you figure the area, then you can calculate Fmax by dividing the Impulse you found by the ms factor from the area you found.

3. Mar 1, 2009

### julz3216

The graph doesn't provide F values so for area i got ((6+2)*Fmax)/2
For impulse I got .06*33 = 1.98 ....(60 g is right -> .06 kg)

But, I don't know what you mean by dividing the impulse by the ms factor?

4. Mar 1, 2009

### LowlyPion

The impulse is change in momentum. That would be twice what you show.

Having found the area under the Force function you have that as 4*Fmax in units of N-s right?

So take the Impulse and divide by the time - 4ms to yield the value of your Fmax looks like to me.

Didn't you say F*Δt = I = Δmv ?