1. The problem statement, all variables and given/known data Find the velocit y and momentum of an electron (rest mass of 0.511MeV) with a kinet ic energy of 10.0 MeV. 3. The attempt at a solution The momentum I calculate using sqrt(2KEm) is giving me a V larger than the speed of light. This can't be true. If I try Rest E + KE = sqrt (m2c4 - p2c2) it gives me a negative root.