1. The problem statement, all variables and given/known data The problem is at http://dl.getdropbox.com/u/175564/physicsSpeedParticles.JPG [Broken] 2. Relevant equations The following equations may be useful E = .5 mc^2 E = Bev 3. The attempt at a solution The right answer is (a). However, I am unsure how it is obtained. For example, by comparing the energies of the two particles, we get only (v1 / v2)^2 = (E1 / E2) * 2/167 where the energies are unknown.