This part of the notes cover how to handle collisions in rigid body simulation.  
There are lots of material covered in this notes. I really enjoyed reading it. Here is a quick summary  

1. How to detect collisions. The idea of the separating plane is quite nice. It is nice how simple methods like these can dramatically improve performance.

2. Handling impacts. Impacts are cases when 2 objects collide then each one goes in its way. (for example, 2 balls colliding). This includes finding the impact point, and then computing the new velocities at impact points. Since we are dealing with rigid bodies, we have to find the new linear velocity AND angular velocity

3. Resting contact. This is when objects are on top of each other in rest. The key point here is to notice that either the velocity at the contact point is zero, OR the reaction force at the contact point is zero. Which means that their product is zero! This gives rise to a very nice quadratic programming problem! Solving it gives the solution to which contact points are actually contact points, and which ones are departing from each other.