Hi, I am trying to work out the result of a collision between two rotating particles if you knew all initial speeds, initial rotation speeds, masses etc. There is no friction or anything complicating. COM: m1v1initial + m2v2initial = m1v1final + m2v2final. COAM: I1w1initial + I2w2initial = I1w1final + I2w2finall. COE: m1v21initial + m2v22initial + I1w21initial + I2w22initial = I1w21final + I2w2finall + m1v21final + m2v22finall. So 3 equations for 4 unknowns . Am I missing anything obvious? Is there another equation I could use was thinking trying to use L= r x mv ? Is there any assumptions I could make to simplify things? Thanks for any help.