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rest mass
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rest mass

physics
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Rest mass is the mass of an object when it is not in motion. In Albert Einstein's theory of special relativity, mass and energy are interchangeable. An object at rest has a "rest energy" of mc2, where m is its rest mass and c is the speed of light. If a body releases energy, its rest mass decreases. This conversion is significant in nuclear reactions, such as the fusion of hydrogen into helium in stars like the Sun. Relativistic mass, assigned to a moving body, increases with velocity and becomes infinite as it approaches the speed of light.123

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5 Britannica Sources
  1. rest mass
  2. E = mc2
  3. relativistic mass
  4. principles of physical science - Developments in particle physics
  5. subatomic particle - Four basic forces

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