# Resulting directions and velocities of two circles colliding

1. Dec 8, 2011

### yortzec

Hi everybody,

I am trying to find the resulting x and y velocities when two moving circles (particles) which are exactly the same and are in the same plane, collide. They are not (necessarily) hitting head on. I am trying to implement this in a 2d computer simulation.

I have the x and y velocities and coordinates of the two particles, but I have not taken a physics class, and most formulas I can find online involve vectors-- I don't entirely understand vectors and can't figure out how vectors can be converted to and from x and y velocities.

Is there a formula to find resulting x and y velocities given the original x and y velocities and the coordinates of the circles at the exact point when the circles meet?

Thank you so much for your help.

-yortzec

EDIT: This post has been moved.

Last edited: Dec 8, 2011
2. Dec 9, 2011

### JHamm

You'll need two things for this; first momentum is conserved (a quick search will do better than any explanation I could quickly type here) and secondly the angles of deflection will be equal to the angles of approach as measured from the point of contact and perpendicular to the tangent of the circles at that point (image might make it a bit clearer)

3. Dec 9, 2011

### yortzec

That is extremely helpful!! Amazing how unnecessarily confusing Wikipedia was when really the answer was that short. Thank you so much, JHamm, I'll try to implement this.