1. The problem statement, all variables and given/known data Find the total energy produced by an electron positron collision each moving at .9c , it is a head on collision. 3. The attempt at a solution Can i just find the relativistic Kinetic energy of one moving at .9c and then double it and add it to their rest energies and this would be the total energy . Or do i need to do Lorentz transformations to see what velocity the one particle perceives the other .