Quote:
Work is being done in the sense that ions are being moved around in your muscle cells to keep the muscle contracted.
|
Yes, to the same degree that it's being done when you're actually moving something. But where does the energy that you use to move something go when you're not strong enough to move it? Or when you're using the same power that you used to move something to just fight gravity?
Quote:
The rope isn't moving, thus it has no kinetic energy. Likewise, no work is done on the rope (although the two guys will grow tired because work is being done within their muscle cells).
|
The rope isn't moving, true, and thus it has no kinetic energy. However, it *is* being applied kinetic energy; it's just that it's being applied
the same amount of energy pulled in opposite directions, thus canceling out. *Obviously* work is being done on the rope, because if they both pull hard enough, after all, they could rip it in two. Yet using the, in this case faulty, work = force * distance equation, you'll still get 'zero work has been done' even if you have ripped it in two and applied massive forces on the rope to do it. The equation is useless for these sorts of scenarios, since it requires that a distance has been covered to get a non-zero result.
Let's say we invented kinetic energy weapons. They shoot a small amount of pure kinetic energy. We're in space, and there's a metal cube or whatever floating directly between two ships which have these weapons mounted. They're at the same distance from the cube, etc. Then, at the exact same moment, both of them fire their weapon at this object. The weapon applies the energy to the entire cube at the same instant.
What happens?