[anon84873628]

Well, a good physics teacher might note the difference between external work on the gravitational field, versus the internal thermodynamic work of the human body. Which could lead to a quick discussion of how muscles are a dynamic system depending on constant activation of actin & myosin (and therefore consumption of ATP) as opposed to a static elastic system like a piece of metal.

Very intuitive analogy is that running an engine in neutral burns fuel, but doesn't do work to move the car forward.