Mass–energy equivalence

E=mc^2

Result unit: J (joule)

What it describes

Mass is a form of energy; even a body at rest has energy equal to mc².

E

energy

[J]

m

mass

[kg]

c

speed of light

[m/s]

Mass is condensed energy. Even a small loss of mass yields an enormous amount of energy (because

c^2

is huge) — this is the source of energy in nuclear reactions and in the Sun.

Nuclear reactions, mass defect, rest energy.

Calculate the rest energy of 1 g of mass.

Substitution

m=0.001

kg,

c=3\cdot10^{8}

Result

E=0.001\cdot(3\cdot10^{8})^2=9\cdot10^{13}

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