rest mass

rest mass

n.

The physical mass of a body when it is regarded as being at rest.

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rest mass

In Special and General Relativity, the observed mass of a body that is not in motion with respect to the observer. Also called invariant mass. Compare relativistic mass.

Thesaurus

Noun

1.

rest mass - (physics) the mass of a body as measured when the body is at rest relative to an observer, an inherent property of the body mass - the property of a body that causes it to have weight in a gravitational field natural philosophy, physics - the science of matter and energy and their interactions; "his favorite subject was physics"