Re: OT: The 10th Demention
 

You're right, I wasn't thinking.

I see what you're saying, but I mean, the 'potential energy' you are talking about is a product of gravity. What when an object's speed does exceed the escape velocity; where does the kinetic energy the object loses on the way out, because of gravity, go? Since the object will never be stopped by that mass's gravity once it's reached e.v. that means no potential energy was created but alot of existing energy was lost, or?

Re: OT: The 10th Demention
 

Its gravitational potential energy. If the object falls down into any gravitational well, that turns back into kinertic energy.

What goes up does *not* have to come back down. That's the point of escape velocity.

You recall those distorted funnel grid paper things that are always used on tv to show gravity fields?
The height represents the potential energy. If the object moves into the depressions, its potential energy is decreasing. In a vaccuum, that pretty much all turns into kinetic energy and back when the object orbits around.

Re: OT: The 10th Demention
 

Perhaps because you can't "rip apart atomic bindings" by pulling on a rope? No amount of force you can apply will overcome the strong nuclear force... Though if you are talking about inter-molecular bonds, those can certainly be broken in the process of applying (thermodynamic) work. But you seem to be thinking of mechanical work...

When you are talking about work, it makes a huge difference which type of work you are talking about. "Work" is a horribly generic word that can mean many different things.

If an object does not move, no mechanical work was done. Mechanical work is purely a derived property of force applied and distance moved. W = F * D is entirely correct, in the mechanical sense of work. Mechanical work does not take heat or other forms of energy transference into account; it only deals with force applied and distance moved.

In the thermodynamic sense of work, you can do work without moving an object. Thermodynamic work is a generalization of the mechanical concept of work; it is a quantity of energy transfered from one system to another. It includes the microscopic thermal motion of particles (aka heat), as well as macroscopic changes to the system (movement, fluid expansion, chemically charging a battery, etc.).

Lets say you decide to push on a wall, which is sturdy enough to resist all of your efforts. Was work performed? No, and yes.

In the mechanical sense, no work was done. The wall was not moved, regardless of how much force you applied. F * 0 is 0.

In the thermodynamic sense, yes, work was done. Your muscles contracted, which required burning up stored carbohydrates and such. This generated heat, which dissipated into your body, the surrounding environment, and perhaps a bit into the wall itself. The force applied on the wall by your hands pushed the wall's molecules ever so slightly inward; this is essentially imparting some kinetic energy from your hands' molecules to the wall's molecules, which in turn is rapidly converted into potential energy. The resulting electromagnetic forces pushed back, resisting any overall change to the structure or location of the wall. In the end, there winds up being no kinetic energy in the wall (when looking holistically at the wall itself). Friction at work (yet another meaning of work... bloody English http://forum.shrapnelgames.com/images/smilies/wink.gif). Hopefully I didn't miss anything there, but you get the idea.

The same exact analysis applies to two people pulling on a rope (without breaking it), save that now you have heat dissipation from 2 people and tension at play. You have lots of thermodynamic work going on, but no mechanical work at all (at least, until the rope breaks).

Re: OT: The 10th Demention
 

Four pages of debate on the principles of physics before Fyron shows up. I was starting to get worried there. http://forum.shrapnelgames.com/images/smilies/wink.gif But now everything makes a lot more sense and I think I might have learned something too, so the wait was worth it.

Now on to more important matters. Why does my beard smell funny after I wash it? It has the same smell regardless of what I wash it with. http://forum.shrapnelgames.com/image...ies/tongue.gif

Re: OT: The 10th Demention
 

So what's really being said is that graivty doesn't create or destroy energy, because it was always 'potentially' there? I.e., potential energy is being treated as existing energy.

Thanks alot for the detailed work explanation Fyron.

Re: OT: The 10th Demention
 

You must not be getting all the accumulated food particles out of it! http://forum.shrapnelgames.com/image...ies/tongue.gif

Re: OT: The 10th Demention
 

The Work performed in washing it was stored as potential energy in the gravitational field. So when it came out as kinetic energy, it had picked up some field odors.

Re: OT: The 10th Demention
 

Field odours! Magnificent! Now all we need is some sort of field odour nulification device to prevent post-shower smelliness. I'd pay a pretty penny for such a device, and I'm sure my brothers in fur would too.

Re: OT: The 10th Demention
 

Oh I like pretty pennies! New technological marvel:
The Covariantly Layered Orthagonally Teathered Hyper Energized Stored Potential Induced Nullifier

http://www.duanekeiser.com/Assets/clothespin2.jpg

Re: OT: The 10th Demention
 

It sounds like implying some wierd things there Raapys.

You do recognize that a spring and a bullet have a fixed amount of potential energy (which are commonly converted into kinetic energy and boing noises, and light, heat and kinetic energy respectively)
Same deal with separated objects in a gravitational field.
Same deal with magnets and electric charges.

Re: OT: The 10th Demention
 

Hmm, I definitely see your point in the spring and bullet scenarios, where it's obvious that there is energy waiting to be released, but with gravity too?

To clarify my question: If we had a device that could read the potential energy we're talking about, then that device would generally, in the case of a compressed spring, come up with the amount of energy used to compress it, right?
But would you also be able to "find" the ( potential ) gravity energy?

I guess my point is, isn't the potential energy of the spring real, i.e. it's actually in the atoms and can be measured, while the potential gravity energy isn't ?

Re: OT: The 10th Demention
 

Why would you think gravitational potential energy is not real?
You drop a bowling ball, and it crushes your toe. That's definitely real energy.

On the small scale, it simplifies to mgh. For larger scales you need integrals. But it is all very straightforward.

The only difference is scale. In the spring, you have electric forces pushing or pulling (but you have to look on the molecular scale). Gravity works on scales big enough to see and just pulls.

BTW, since gravity is always attractive, the arbitrary zero point is generally placed at infinity. So if you fall inwards, your gravitational potential becomes negative.
Conveniently, setting the point there means that if your total energy is positive, you can escape. If the total is negative, you're stuck in the gravity well unless you steal some energy from something else.

Re: OT: The 10th Demention
 

I think what is trying to be said is that if we understood enough about gravity we could potential control it and generate a "limitless" supply of PE since gravity only weakens over distance and not time.

Re: OT: The 10th Demention
 

*Sigh*

Re: OT: The 10th Demention
 

I realize the point you're trying to get across, but the end all be all is the fact that the mechanism behind gravity is still a mystery. The definitions of energy are left intentionally vague because we don't understand them completely.

Gravity is a property of matter, but how is it "enforced." That's where gravitons come in.

Re: OT: The 10th Demention
 

ALL the fundamental forces do not fade with time. Gravity is nothing special.

The only reason why everyday forces fade is because they do work on stuff and thus dissipate the energy into the environment.
If you don't let your Bowling ball fall, it dosen't lose any potential energy. If you don't let your spring expand (or rust out!) then it dosen't lose any energy. If you don't let your flywheel interact with the environment, it won't slow down, but it will still be exerting a lot of force to keep the outer edge of it moving in a circle.

Conversely, if you use a realistic flywheel, the bearings will introduce friction and sap your kinetic energy into heat and noise.
If you use a realistic spring, it suffers chemical reactions, and metal fatigue.
If you have your bowling ball sitting outside, it will sink into the mud.

Re: OT: The 10th Demention
 

I'm just not sure what the difference would be between saying that "This object has potential gravitational energy that is being transformed to kinetic energy as it approaches another mass" and saying that "Gravity creates kinetic energy in this object as it approaches a mass, or destroys it as it moves away from a mass".

The first one corresponds with the energy conservation law, the second one does not. Can it actually be proven that the first one is more true than the second?

The reason I mentioned potential gravitational energy not being real is because it can't be put on a weight. I mean, you can weigh 'normal' energy, since it actually has mass, but gravitational potential energy doesn't, to my knowledge.

Re: OT: The 10th Demention
 

There is a huge body of empirical evidence supporting the veracity of the conservation of energy law.

Re: OT: The 10th Demention
 

Veracity is one of my favourite words.

Re: OT: The 10th Demention
 

"Constants aren't. Variables don't."

Paul Dirac speculated about the gravitational "constant" varying over time all the way back in 1938. This article lists the current upper bound for how fast it could be changing. Some versions of string theory allow for the possibility that other "constants" also change over time.

Re: OT: The 10th Demention
 

That's not what we were talking about.

Gravity and electromagnetism don't run down like a battery.