1. The problem statement, all variables and given/known data The mass of a proton when at rest is m. According to an observer using the detector frame, the speed of the anticlockwise moving bunch, A, is such that va^2/c^2=24/25 Show that the total relativistic energy of a proton in bunch A, as observed in the detector frame, is exactly 5mc^2, and work out the speed of the proton, expressed as a decimal multiple of c, (to 5 significant figures). 2. Relevant equations Right I think its these E=mc^2 Etot=mc^2/√1-v^2/c^2 Etrans=mc^2/1-v^2/c^2 and maybe E^2tot=p^2c^2+m^2c^4 p=mv/1-v^2/c^2 3. The attempt at a solution Now I know that to get Etot you need e=mc^2 and Etrans and so maybe combing these equations will give the answer but I think this IS not the right to get 5mc^2. So maybe its E^2tot equation I have to use. Im just not sure.