In our introduction to energy, we talked about how forces can act on an object to do work.  We can keep track of total amount of work done on an object using the work-energy theorem and, as more and more work done on the object is done by conservative forces, using the principle of conservation of energy becomes increasingly useful to describe an object’s motion.  All of that still holds when thinking about how forces act on an extended object.  We can calculate the rotational work done by a force as it generates a torque about some axis.  If we need to, we can use the total rotational work done on an object to keep track of how its rotational motion changes through the work-energy theorem.  And most importantly, we have another form of kinetic energy that energy can be converted into in a conservation of energy problem.