So this is possibly a misunderstanding of the meaning of work, but all the Physics texts, sites, and wiki that I've read don't clear this up for me:
In the simplest case with the simplest statement, work is force times distance. If you push with a force $F_{1}$ on an object that doesn't budge because of friction, you do no work. If your friend helps push and you still apply the same force $F_{1}$ and the thing moves, all the sudden you're doing work and it's not really because of what you're doing. Moreover, if you continue applying the same force, and your friend increases her force so that the thing moves faster, and covers a greater distance, again you're doing more work and by no fault of your own.
This just seems paradoxical, and maybe the only sensible answer to this paradox is "Well, the physical notion of work is not the same as the everyday notion of work," but I'm wondering if anyone can say anything about this to make it feel more sensible than just accepting a technical definition for a word that doesn't seem like the right word to use.
Answer
If you're pushing a 10-ton truck and it's not moving, you are not doing any work on the truck because the distance $ds=0$ and the nonzero force $F$ isn't enough for the product $F\cdot ds$ to be nonzero.
Your muscles may get tired so you feel that you're "doing something" and "spending energy" but it's not the work done on truck. You're just burning the energy from your breakfast by hopelessly stretching your muscles. The energy gets converted to heat and your body is really losing it, but when we talk about "work", we usually mean "mechanical work" done on an external object, and it is zero.
If someone loosens the brakes and you suddenly manage to move the truck, your perception how "hard" it is may be the same as before. You may be spending the same amount of energy obtained from the breakfast. But there is a difference. A part of this energy is converted not to useless heat of your muscles but to the kinetic energy of the truck.
Your impression that the work changes "not because of what you're doing" is an artifact of the fact that a big part of the energy is spent on heat in the muscles in one way or another. But it's really the usefully spent part of the energy, however small, that does the mechanical work. It may be a small part so it may be hard to notice it.
Physical terms often deviate – and they are more accurate than – their counterparts in everyday English (or another language). But I would argue that the physics definition of (mechanical) work does agree with the everyday life usage. If you're hired to do some work with the truck and move it and the truck doesn't move an inch, your boss will conclude that you haven't done your work and you won't be paid a penny, just like what physics seems to calculate. You may have spent your energy by stretching and heating muscles but that's not called (mechanical) work. Work is actually supposed to be something useful – both in everyday life and in physics. In both cases, the conversion of energy into useless heat isn't included to "work".
Just to re-emphasize this insight. There are many forms of energy and work and many "quantities with the units of one joule". But the words denoting them are not synonymous. So energy isn't quite the same thing as work and it isn't the same thing as heat or mechanical work or something else (also, debt and profit aren't the same despite the same unit of one U.S. dollar). The energy conservation law says that the sum of several quantities of this kind are zero or equal etc. but the different terms have to be distinguished and in these contexts, "work" really means "mechanical work".
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