Suppose I have an object resting on top of a table. There are two forces acting on the object: gravitational pull and the supporting force from the table. It is pretty obvious, that the table is doing no work, because the supporting force has no displacement. However, in a moving coordinate system the point where the force acts actually has displacement, therefore the table does work on the object. Now a table obviously cannot transfer energy by itself. My question is how do I determine the actual work done by the table, on what basis do I differentiate between the resting and moving coordinate system to calculate the work being done?
The question arose when I was taking an escalator and moving up the stairs. Assuming that I'm moving with the same relative velocity compared to the escalator do I need to invest the same amount of power as if the escalator was stationary?