Rest energy
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The rest energy E or rest mass-energy of a particle is its energy when it is not moving relative to a given inertial reference frame. It is defined by
- E = m0c2
where m0 is the rest mass of the particle and c is the speed of light.
The equivalence of mass and energy can be derived from the Special Theory of Relativity. The mass of a given body is appeared to be increased when it moves faster. Change in mass is equal to its change in kinetic energy divided by speed of light square.
It seems that the mass of a body increased if it gets more kinetic energy. This implies that energy and mass are actually equivalent and identical. Therefore, a particle which remains at rest to a given inertial frame of reference would have certain amount of energy if it has mass. Just like any other forms of energy, rest energy can be converted to other forms of energy. This implication has been proved by nuclear reactions. In nuclear fission reaction, total mass-energy is conserved but rest mass-energy is decreased. It is converted into other forms of mass-energy such as kinetic mass-energy.
