# Homework Help: Elastic collision

1. Sep 8, 2010

### thereddevils

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

A body of mass, m makes a head on perfectly elastic collision with a body of mass, M initially at rest. Show that

$$\frac{\triangle E}{E_o}=\frac{4(\frac{M}{m})}{(1+\frac{M}{m})^2}$$

2. Relevant equations

3. The attempt at a solution

Momentum: $$mu_1=mv_1+Mv_2$$

$$\triangle E= \frac{1}{2}mv_1^2+\frac{1}{2}Mv_2^2-\frac{1}{2}mu_1^2$$

2. Sep 8, 2010

### Staff: Mentor

If collision is ellastic, delta E as defined (final minus initial, right?) should equal zero.

Or am I missing something?

3. Sep 8, 2010

### thereddevils

Thanks Borek! Exactly, i think it's meant to be inellastic collision. I'll give it a try.