Assume I have two disks, $p_1$ and $p_2$, of radius $r$, with their own velocities (preferably in $(x,y)$ form, but $(m, \theta)$ works too) and masses (unit-less, but same unit) collide in two dimensions, how can I compute their resulting velocities?
I was looking around on the internet and it seems like every calculation assumes that one of them is at rest, but both of mine will be moving.
Wikipedia has this bit, but it assumes that I know how to calculate the angle of deflection of the system, $\theta$, but that's even more confusing.
I'm pretty lost. What do I do?