Special Relativity - Relativistic Energy

What is the speed of a particle having a momentum of 5 MeV/c and a total relativistic energy of 10 MeV?

A. c
B. 0.75 c
C. 1/√3 c
D. ½ c
E.  ¼ c

(GR9677 #38)

Solution:

p = γm₀v
E = γm₀c²

p/E = v/c²
v = pc²/E = (5 MeV/c) c²/10 MeV = ½ c

Answer: D