## College Physics (4th Edition)

$p = 6.48~MeV/c$
Mote that the rest energy of an electron is: $mc^2 = 0.511~MeV$ We can find the momentum $p$: $E^2 = (pc)^2+(mc^2)^2$ $(pc)^2 = (6.5~MeV)^2 -(0.511~MeV)^2$ $(pc)^2 = 42.0~(MeV)^2$ $pc = \sqrt{42.0~(MeV)^2}$ $pc = 6.48~MeV$ $p = 6.48~MeV/c$