Hey so I recently started learning physics, and came upon this wonderful site that taught me how to calculate 2D collisions between two circles.
The only part I'm confused about is how the velocity vectors are translated back to the original coordinate system from the cm frame. The equation can be seen in the self-explanitory code in the picture below:
(phi is the angle of the line that goes through both circle's centers)
**Why is this equation different from the first on used to rotate the points to the new 1D coordinate system? And why is the +180/2 added into the reverse rotation equation?
How is it that force only travels along the phi line? Is there a law that explains this?