I've been using this document to learn how to implement a very basic physics engine. The section on Coulomb Friction on page 55-56 (marked as pages 43-44) confuses me.
It observes that the friction force can be calculated using the collision impulse (
jr). This seems strange. Envision an object falling very quickly onto a plane with a slight incline. The object is rotating in the opposite direction it would if it were rolling down the incline. When the object makes contact, it will have a small velocity along the tangent, but a huge normal impulse (
jr). This will result a very large change in velocity along the tangent (
t hat) opposite to the direction of motion. This will push the object up along the surface (bad!) with a notable amount force. My implementation confirms this.
Can someone explain to me how this all fits together? I'm very confused.
P.S. I don't think trying to provide an example of my implementation here is relevant, either the effect I'm explaining cannot occur (in which case there is a bug, which I can find myself), or I'm misunderstanding the equations, in which case the implementation is inherently broken