Now that we can track the motion of the center of mass of a system, we can start to ask what additional motions is the system capable of.  What we will see is that the motion of our system can be broken up into two pieces, the motion of the center of mass of the system and the motion of the pieces of the system about its center of mass.  This sets the stage for considering extended objects where we can talk about the translational motion of the center of mass and the rotation of the object about its center of mass.  As a result, we will basically revisit all of the concepts we have seen so far, just extending them to talk about the rotational motion of rigid bodies and how forces act to cause extended objects to rotate.