# Coefficient of Restituion

1. Feb 2, 2016

### Revengeance

1. The problem statement, all variables and given/known data
So we are doing a lab that is basically finding the coefficeint of restituion, what we did in this lab is drop a tennis ball from an initial height (recorded that height) and timed it until it stopped bouncing. So we have the time it stopped bouncing at and the height, and now we have to find the coefficeint of restution.

So I am guessing the two bodies in this situation is the ball, and the floor?

2. Relevant equations
e = (v2final - v1final / v2initial - vinitial)

3. The attempt at a solution
So i know that v2f - v1f is equal to the velocity of seperation, which is the veloicty of the ball and second body after the collision, and v2i - v1i is the velocity of the ball and second body before the collision. Before i move further i would like to have help figuring out the second body in this collision.

2. Feb 3, 2016

### Staff: Mentor

The rebound speed of the Earth can be assumed zero.

You have recorded the time to execute a number of bounces?

3. Feb 4, 2016

### J Hann

Since the speed of the earth is zero e = -V1 / V0
From this you can show that e = (h1 / h0)^1/2 or h1 = e^2 h0
and h2 = e^2 h1 = e^4 h0 and hn = e^2n h0
Now, can you use this to find and expression for tn ?

4. Feb 4, 2016

### Staff: Mentor

What is tn and why do you need to determine it? You still haven't explained exactly what data you recorded; I think it would be difficult to sense precisely the moment that a ball takes its final "bounce", and it's not clear how you would use that moment.

5. Feb 4, 2016

### Staff: Mentor

I suspect that the time between bounces follows a sequence that has a finite sum, and that the sum depends upon the coefficient of restitution (among other things). So if you determine a time that the ball finishes bouncing (at least perceptibly to the observer), then you can determine a value for the coefficient.

6. Feb 4, 2016

### Staff: Mentor

I was inviting OP to post the maths he has on this; most likely it has been discussed in class or homework.

7. Feb 4, 2016