# Trouble understanding non-conservative force and work

I am having some trouble defining whether a force is conservative or not. In the example that we are working on a mass on a pulley system is used to cause a slender bar to rotate from rest to a certain angle. I know that the tension forces in this case are conservative but I was wondering what force, if any, was non-conservative?

The simplest example for a non-conservative force is frictional force. For example, to move an object from point A to point B on the table we would require say $10$ J of energy, now to put it back to point A, we would need same $10$ J of energy. Practically nothing observable has changed, but we've performed $20$ J of work, which went to overcome frictional force. So, we may conclude that it is non-conservative. (Since we cannot assign points of potential for it)