In my Java2D simulation, I have a disc which, when it bounces off the boundary of a 2D region, begins to rotate, as if it had gotten some spin from the wall.

The situation

I'm having trouble relating the collision vectors and the angular velocity of the spin that should result.

How should I approach this?

  • \$\begingroup\$ The first answer says 'cross of incident and normal'. Its unclear if its velocity vector or position vector. \$\endgroup\$ Feb 2, 2014 at 17:57
  • \$\begingroup\$ It has to be the velocity. Position vectors are always rooted at 0,0 and so their direction doesn't have much meaning. (Consequently, crossing them with something wouldn't do anything very interesting.) \$\endgroup\$
    – Anko
    Feb 2, 2014 at 20:05


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