# Atwood machine bounce, how high?

1. Jun 9, 2010

### Uku

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

Basically, an ideal Atwood machine is released from rest (m1 != m2) and I have to find out how high the mass, say m1, bounces after an absolutely inelastic collision with the floor (no energy is lost).

2. Relevant equations

Conservation of energy, Newtons equations.

3. The attempt at a solution
Well, I can find the velocity of the system when it hits the ground in two ways, cons. of energy and by using Newtons II'nd law. The first one is preferred since it does not include time in it. Now, using this velocity I should be able to find how high the system bounces after the collision, but I'm a bit lost on that. Where look and how to do?

2. Jun 9, 2010

### Staff: Mentor

You can find the height reached using the same principles: conservation of energy or kinematics. Realize that once it bounces, the mass is just a projectile like any other.

3. Jun 10, 2010

### inky

Hi Uku,
Your problem is difficult to understand. In inelastic collision, energy is always lost. You may use no energy lost for elastic collision.
After collision, at the maximum, velocity=0

4. Jun 10, 2010

### Staff: Mentor

I'm sure that inelastic was a typo and that elastic is what was meant.

5. Jun 10, 2010

### inky

Problem mentions the inelastic collision. If it is perfectly elastic collision, coefficient of restitution between floor and the mass is 1. I consider for e=squareroot of h2/h1.(short method)