1. The problem statement, all variables and given/known data Suppose you have two 2D circles, where size ≈ mass, each of which is moving with known x- and y-velocities. The two collide, not necessarily head-on (one could broadside the other, etc). How do I calculate the resultant velocities, assuming no elasticity or friction? 2. Relevant equations ρ = mv m1v1 + m2v2 = m1v1` + m2v2` Speed = Square root of (X-velocity^2 + Y-velocity^2) 3. The attempt at a solution Each circle is moving in a particular angle (direction), and hits the other at a particular angle. If the difference between angles is 0, then the mower transfers all of its momentum to the other. If the difference is approaching 90 degrees, then the amount transferred is approaching 0. I apologize if this has already been answered; I couldn't find it. Thanks!