Mass-Energy Equivalence

Mass and energy are two forms of the same physical quantity, so a body at rest still has an intrinsic amount of energy because of its mass. The factor c^2 is enormous, which is why even a tiny amount of mass corresponds to a huge amount of energy. This relation comes from special relativity, where the total energy of an object increases with its motion and reduces to E = mc^2 when the object is at rest.

Use this formula when you need the energy equivalent of a given mass, such as in nuclear reactions, particle physics, or estimating energy released by mass loss. It is also useful when comparing tiny mass changes to the very large energies they represent.

• Using grams instead of kilograms in the calculation
• Forgetting that c must be squared
• Thinking the formula only applies to moving objects rather than rest mass