- Center of mass coordinates
In
kinematics , both classical or relativistic, the center of mass coordinate system is acoordinate system in which thecenter of mass of the system remains still (it has novelocity ). It is especially useful for the kinematic study of an assembly of particles.We shall note a variable in the center of mass system with a bar over it, so that, e.g., by definition.
In any coordinate system,
:
where the sum extends over the index of particles with mass and velocity . From the previous equation we see that in the center of mass system, the total
linear momentum p is therefore zero::
where .
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