1. The problem statement, all variables and given/known data Electrons are accelerated by a potential difference of 0.10 MV. Determine: a) The mass an accelerated electron b) The velocity of an accelerated electron The mass of the electron has been successful determined, which I give here. I was doing wrong when I was counting the speed based on the rest mass of the electron. Here, I would like to be sure that qU = 0.5v^2 is correct based on the relativistic mass. I have problems in this course, because I get questions that I've never seen before. 2. Relevant equations qU = mc^2 – m0c^2 qU = 0.5mv^2 3. The attempt at a solution a) 100'000 V = 1.602*10^-14 Joule m0c^2 = 8.18751672*10^-14 Joule 1.602*10^-14 = (8.18751672*10^-14) - mc^2 mc^2 = 9.78951672*10^-14 m = (9.78951672*10^-14) / c^2 m = 1.08917583*10^-30 kg This far I know the relativistic mass is correct, easy task. b) I try to use the relativistic mass in this formula: qU = 0.5mv^2 1.602*10^-14 = 0.5(1.08917583*10^-30)v^2 v^2 = 2.941673798*10^16 v = 171’513’084 m/s Here, I’m not so sure that this is the right way. I only do believe so. I’m thankful for answers.