OT: The 10th Demention

[Raapys]

But you're keeping your muscles contracted *to keep the thing from falling to the ground*, thus you are, for that entire hour, applying more and more kinetic energy to the box. Put it like this: if the gravity was to suddenly vanish, the box would go flying off from the force you were exerting on it at that given moment. You're not exerting any less force on it just because it's not moving.

[Suicide Junkie]

It would drift off very slowly.

It starts at rest relative to you and the surface of the Earth, and you will be pushing 9.8m/s^2 for maybe 1/10th of a second before you notice and stop pushing.

You aren't actually adding any kinetic energy to the box.
Work = force * distance.

Effort feels more like force * time, but it dosen't have any serious meaning.

[Raapys]

But the 'work = force * distance' function is fatally flawed when used in this situation, because the result of the equation will be zero, indicating no energy has been spent, no work has been done. Obviously this is completely incorrect, since you'll be standing there sweaty and tired, having wasted alot of energy on the task.

I think a fitting metaphor would be two guys pulling each side of a rope. They're both applying kinetic energy to the rope, but in different directions, canceling it out. So even if the rope isn't actually moving, there's still alot of work being done on it. The difference is that where both these two guys would eventually get tired, gravity does not.

Hmm, I guess one solution would be that the force you're using to hold the box up is simply being applied as kinetic energy to the *Earth*, thus seemingly 'disappearing' since it's hardly noticeable for something on that scale.

[se5a]

they're not applying kinetic engergy, it would be... burning organic matter and turning it into heat mostly.
I think...

[Spoo]

Raapys said:
But the 'work = force * distance' function is fatally flawed when used in this situation, because the result of the equation will be zero, indicating no energy has been spent, no work has been done. Obviously this is completely incorrect, since you'll be standing there sweaty and tired, having wasted alot of energy on the task.

Work is being done in the sense that ions are being moved around in your muscle cells to keep the muscle contracted.

I think a fitting metaphor would be two guys pulling each side of a rope. They're both applying kinetic energy to the rope, but in different directions, canceling it out. So even if the rope isn't actually moving, there's still alot of work being done on it. The difference is that where both these two guys would eventually get tired, gravity does not.

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).

[Raapys]

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?

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?

[Phoenix-D]

GuyOfDoom said:

Admittedly I've never read Origin of Species, but I don't believe he states where life started, which is a large misconception. As for his theory being wrong, I'm confused as Evolution happens, but not precisely in the way he was able to observe at the time.

No, I don't think he did. However the view of evolution posited in that book has gone through so many revisions I feel quite comfortable in saying he was wrong.

[Suicide Junkie]

The ripping process eats up a lot of energy in the breaking of bonds and a bit in the final acceleration of the two halves of the rope.

In the ship example, presuming the block and shots all stick together, you end up with a block with two bullets in it, and two ships both moving away from the block.

The thing you're not getting is that you don't "apply kinetic energy" to anything. You exert forces. The force may be countered by friction or an opposing force.
You can waste energy all you want, you'll just get hot and sweaty without getting the result you wanted.

[se5a]

we don't need to "invent" a kenetic energy weapon, we've already got them, that is precicely what a rifle is.
an object has kenetic energy when it is moving.
when it is at rest, it has no kenetic energy.

[GuyOfDoom]

Phoenix-D said:

No, I don't think he did. However the view of evolution posited in that book has gone through so many revisions I feel quite comfortable in saying he was wrong.

True enough. Darwin is too often credited with the "origin theory" of evolution when it really doesn't have anything to do with the origin of life.