Kinetic energy: ek = e-E0 = 5-0.512 = 4.488mev.
Momentum: p = (sqr ((e) 2-(E0) 2))/c = sqr ((5 *1.6 *10-13) 2-(0.512 *)
Speed: v = c * sqr ((e 2-e 02)/e 2) = 0.9947c.