Center-of-momentum frame

Unique inertial frame in which the total momentum of a physical system vanishes

In physics, the center-of-momentum frame, also known as zero-momentum frame, is the inertial frame in which the total momentum of the system vanishes. It is unique up to velocity, but not origin. The center of momentum of a system is not a location, but a collection of relative momenta/velocities: a reference frame. Thus "center of momentum" is a short for "center-of-momentum frame".

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