Some notes made during making the collision demo

Written by Nasser M. Abbasi

June 28, 2015

Given 2 particles $v,u$ with velocity components as shown.

In elastic collision linear momentum in the $x$ and $y$ directions holds

In addition, kinetic energy is constant. Let $v21 = (v21x +v21y)$ , $v22 = (v22x + v22y),V12= (V12x + V12y)$ , $V22= (V22x + V22y)$ then

We have 3 equations above, but 4 unknowns $(V1x,V1y,V2x,V2y)$ . The 4th equation comes from knowing that after collision, particles will travel at $0 90$ trajectories.