Einstein's theory of relativity predicts that a body of mass m0 at rest has mass: m = m0/√(1-(v^2/c^2)) , where c is the velocity of light and v is the velocity of the body.
Use a series to obtain the approximation: mc^2 ≈ m0c^2 + 1/2m0v^2
Other Info that may be needed:
1. Mass energy formula: E = mc^2
2. Kinetic energy of a body at rest: v = 1/2m0v^2 (where mass is m0 and velocity is v)