Is the work-energy theorem valid for only particles or rigid bodies as well?
Most places where I have read this seem to claim the latter. But an example I thought up has been troubling me.
Consider a block resting on a rough surface. We apply a force on the block. The force is balanced by friction and the block does not move. However, the force is such that the point of application of the force moves on the object. Thus work is done by this force on the object. However, the kinetic energy does not change seemingle violating the theorem.
Is there some flaw in my reasoning or is the work kinetic energy theorem valid really only for particles?
EDIT: To be clear, I am describing the simplest form of the work kinetic energy theorem, the one for a single nonrigid body. I don't believe things like internal energy and potential energy need to be invoked in such a case. Or do they?