Enter the mass of an object at rest to calculate its total equivalent energy while at rest.

Rest Energy Formula

The following formula is used to calculate a masse’s rest energy.

E0 = m*c2

  • Where E0 is the rest energy (J)
  • m is the mass of the object (kg)
  • c is the speed of light ((299,792,458 m/s))

Rest Energy Definition

Rest energy is defined as the energy equivalent or amount of energy contained within a mass if that mass was converted purely to energy.

Sometimes this is referred to as the energy of a particle in the inertial frame of reference. The inertial frame is that of a particle with no external forces or movement acting on it.

Example Problem

How to calculate rest energy?

  1. First, determine the mass of the particle.

    For this example, we will be looking at a small sphere with a mass of 2kg.

  2. Next, ignore any external forces or movement of the particle.

    This will confirm we are looking at the particle in the inertial frame of reference.

  3. Finally, calculate the rest energy.

    Calculate the rest energy using the formula e=mc^2 = 2* 299,792,458 =599,584,916 Joules.

FAQ

Are rest energy and relativistic energy the same?

The terms rest energy and relativistic energy are used interchangeably to mean the equivalent amount of energy contained within a specific mass.

How does mass have energy?

According to Einstein’s Theory of Relativity, mass can be converted to pure energy and energy can be converted to mass. They are one and the same, hence the formula E=mc^2.

In more practical terms it’s extremely difficult or near impossible to convert easily between the two forms of matter. For example, nuclear fission and nuclear fussion are two ways that matter and energy are created.

In nuclear fission, atoms are split apart and the result is a release of a vast amount of energy and a slightly smaller mass. In nuclear fission, atoms are combined together and the result is also a slightly smaller mass and a release of a large amount of energy. The small missing mass was converted to energy in these cases.