Relativistic mechanics
In Einstein's relativistic mechanics
(used especially for near-light velocities)
the kinetic energy of a body is
where:
Ek is the kinetic energy of the body
v is the velocity of the body
m is its rest mass
c is the speed of light in a vacuum.
γmc2 is the total energy of the body
mc2 is the rest mass energy (90 petajoule/kg)