Hello, I was wondering what a collision between two (elementary) particles looks like exactly. Most classical mechanics formulas seem to describe larger systems and their rules may not necessarily be the same. So I had several questions: Can the same formulas of larger bodies about force, acceleration, velocity, momentum and such be translated down to single particles perfectly? If two particles have different momenta, will their eventual momenta always lie closer together? Will it always completely average out, or is there room for partial momentum changes? If two particles have identical momentum, will they always leave the collision at identical momentum? Or can properties such as spin or even the spinaxis affect the momenta in such a way that they might go apart a bit?