I'm having some trouble wrapping my head around a couple work concepts. I've been reading the following thread: https://www.physicsforums.com/threads/displacement-and-work.322461/ and I don't think I've fully grasped how work is accomplished. My first question is if I lifted a (w=3.0N) water bottle 3.0m vertically and the returned it to its original position, has work been done? I realize that work is done from lifting and lowering it down, but once it returns to its origin does it matter? The second is if two people press against a wall and person A gives up twice as person B then have persons A and B accomplished any work? And if so then has person B accomplished more for pushing longer? I realize that straining your muscles in any way requires energy, especially for long periods of time, but in a physics sense (We're talking college physics I) does it matter?