Energy & Mass Equivalence (Cambridge International A-Level Physics)

Energy & mass equivalence

• Einstein showed in his theory of relativity that matter can be considered a form of energy and hence, he proposed:

  • mass can be converted into energy
  • energy can be converted into mass

• This is known as mass-energy equivalence, and can be summarised by the equation:

E = mc²

• Where:

  • E = energy (J)
  • m = mass (kg)
  • c = the speed of light (m s^-1)

• Some examples of mass-energy equivalence are:

  • the fusion of hydrogen into helium in the centre of the sun
  • the fission of uranium in nuclear power plants
  • nuclear weapons
  • high-energy particle collisions in particle accelerators