help with velocity in relativistic momentum??? a proton has 1836 times the rest mass of an electron. At what speed (in c) will an electron have the same momentum as a proton moving at .0180c? -- here's what i have so far------------------------ 1. by using the mass of a proton i determined the momentum of the electon as p proton= p electron p proton= (1.673e-27 * .0108*3e8)/(1-.0108^2)^1/2 p proton= 9.035e-21 i am having trouble converting the equation p= m1*v1/(1-(v1/c)^2)^1/2 into an equation that i can use to find the velocity of the electron. All of the answers i get seem to put c well over one... any ideas? any help would be greatly appreciated.