Two electrons, each with mass mmm and charge qqq, are released from positions very far from each other. With respect to a certain reference frame, electron A has initial nonzero speed vvv toward electron B in the positive x direction, and electron B has initial speed 3v3v toward electron A in the negative x direction. The electrons move directly toward each other along the x axis (very hard to do with real electrons). As the electrons approach each other, they slow due to their electric repulsion. This repulsion eventually pushes them away from each other.

What is the minimum separation r_min that the electrons reach?