The velocity of a proton emerging from a van de graaff accelerator is 25.0% of the speed of light. what was the equivalent voltage through which it was accelerated? the mass of a proton is 1.67 x 10^-27kg1.67×10 −27 kg. (recall that the kinetic energy gained is equal to the electric potential energy lost as a charged particle moves through ad potential difference, ie. q delta v = delta keqδv=δke.)