1. The problem statement, all variables and given/known data For an electron having energy 1.5MeV/c (mass of an electron is 0.5MeV), the velocity is given by? a) 2.92x1010 cm/sec b) 2.81x1010 cm/sec c) 2.75x1010 cm/sec d) 2.50x1010 cm/sec 2. Relevant equations Kinetic Energy = 0.5mv2 3. The attempt at a solution I first converted energy into joules and mass into kg. E=2.4032x10-13 and mass = 8.91331x10-31. Then I put it into the equation for kinetic energy and solved for v which yields the result v = 7.3432x1010 cm/s which is not among the choices. Then I observed that energy is not given in simply eV, at the end there is MeV/c. I am unable to understand what this means. It would unbalance the units on RHS. Is there another formula to be used instead of KE and what does MeV/c mean?