1. The problem statement, all variables and given/known data In reference frame S', two protons, each moving at .5c, approach each other head on. A) Calculate the total kinetic energy of the two protons in frame S'. B) Calculate the total kinetic energy of the protons as seen en reference frame S, which is moving with one of the protons. 2. Relevant equations K=(mc^2/sqrt(1-(v/c)^2))-mc^2 3. The attempt at a solution I have no attempt. I have no idea where to start.