# Relativistic collisions

1. Mar 8, 2015

### 1bigman

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

We have a particle mass $m$ with kinetic energy $k$ colliding with a stationary particle of mass $2m$. The collision creates a composite mass of $\sqrt{17}m$. Find the value of $k$

2. Relevant equations

3. The attempt at a solution

I have tried using mass-energy conservation and also momentum conservation, but I can't seem to get the required result of $k=2mc^2$

2. Mar 8, 2015

### vela

Staff Emeritus