1. The problem statement, all variables and given/known data A particle of rest mass 1.30 MeV/c2 and kinetic energy 2.70 MeV collides with a stationary particle of rest mass 2.50 MeV/c2. After the collision, the particles stick together. Find the speed of the first particle before the collision 2. Relevant equations [tex]KE=(1-\gamma)mc^2[/tex] 3. The attempt at a solution I am positive this is the right equation to use but I keep getting the wrong answer. I don't know why!