1. The problem statement, all variables and given/known data On attachment. Part B only. I got C. 2. Relevant equations mass of proton is 1.673*10^-27 q0 = 1.60*10^-19 3. The attempt at a solution For part B I thought I could divide the intial speed by 2 and plug it back into the energy conservation equation: .5mv^2 + q0V1 = .5mv^2 + q0V2 and solve for (V1 - V2) which would be the potential difference but it doesn't seem to work.