# Rest mass

From AMS Glossary

## rest mass

(Also called proper mass, invariant mass, velocity-independent mass.) The mass of an object measured in a coordinate system in which the object is at rest.

To retain within special relativity the classical form of Newton's dynamical law of motion for a body with momentum momentum may be written as The relativistic mass is defined as where

**p**and velocity**v**acted upon by a force**F***m*is the rest mass and*c*is the free-space speed of light. For meteorological applications, rest mass and relativistic mass are so nearly identical that it is largely pointless to make a distinction between the two.Helliwell, T. M. 1966. Introduction to Special Relativity. 148–150.