1. The problem statement, all variables and given/known data How much work is required to accelerate a proton from rest up to a speed of 0.999c? What would be the momentum of this proton? 2. Relevant equations p=γmv 3. The attempt at a solution I got part A, which was the momentum. I found that to be 20.1 GeV. Now for part B I have to find the momentum in units of GeV/c. I'm down to my last attempt on Mastering Physics. First, I tried going the simplest route and divided the 20.1 GeV from part A by c to get 6.7e-8 and that was wrong. I also tried using p=γmv to find an answer of 1.12e-5 J, which I converted to 7.01e-8 GeV, then divided that by c and got an incorrect figure of 2.34e-16. Any help would be greatly appreciated.