TITLE: How can I visualize the center of mass (center of momentum) frame?
QUESTION [0 upvotes]: I know that the CM frame is the frame in which the total momentum of the system adds up to zero.
For example, if I imagine two bodies m1 and m2, with m1 = m2, one moving at the speed v1 = v and the other standing at v2 = 0, we can say that in the CM frame they are both moving at the speed of |v*| = |v/2|.
How can I mentally visualize the position of the observer that sees both bodies moving at that speed? I think the observer should move at a certain speed too, but which speed?

REPLY [1 votes]: Visualize the point half way between m1 and m2. Since m1=m2 that is where the CM always is. As V.F. said, it moves with speed v/2.
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