Gravity as an energy source?

[YT2095]

the movement was caused by the "Trigger" that overcame the friction holding the magnet in place, the magnet was simply trying to attain Rest again releasing the potential energy stored in its elevation from whatever put it up there in the first place.

[gcol]

1.

I took it as a given that the slug would have to acquire potential energy by working it against gravity. I was just imagining that all the gravitically stored kinetic energy would be converted to electrical work.

 

2.

Must be a magnet? I was thinking of eddy currents induced, tiny effect at first, by the local domains caused by molecular dipoles, Where any imbalance might result in the slug becoming uniformly magnetised by the time it came (momentarily) to rest. Certainly easier and quicker to start with a magnet though.

[pHoToN_gUrL]

How about moving up a small magent, and dropping it in to a very long coil. This creates electricity (current flow), from the gravitational acceleration (gravitational kinatic energy) of the magent, in side the coil. Since the coil has a current inside it, magnetic filed will be created around the coil. This magnetic filed will oppose the pull of gravity on the falling magnet. So the magent will start boucning up and down. This up and down movement of the mass could be used to do mechanical work. I bet this is efficint since we only needed to spend a little enegy moving the small mass (magnet) to the top of the coil. Feedback please.

[YT2095]

PG, actualy what you describe there sounds very similar to how a swing arm (moving coil or moving magnet) meter works

 

yes it`s a perfectly sound principal, but has little to do with gravity.

 

there is also something called magnetic damping also, again, that has little to do with Gravity as such and all to do with movement.

 

in Any of those ideas mentioned, you could replace gravity with an elastic band or a wound spring.

gravity alone is a loose band or spring, it has not inherant Energy of its own.

[wpenrose]

....But what i am most curious about at this point is that, how would you go about generating electricity from gravity?

 

Here's a puzzler for you.

 

Actually, it stumped two eminent physicists that I know, for a short time. Yet the answer, once you realize it, is obvious.

 

Imagine a hydroelectric plant. It operates from a body of water located at some altitude. The energy is 'stored' in the difference in height between the water at the top and the water at the bottom spillway. Now, when the plant is operating, you have a mass of water rushing down the tube to the turbines at the bottom. But the water entering the turbines is the same mass and velocity as the water exiting the turbines. So when you plug your TV into the turbine and it lights up, where does the energy come from?

 

Dangerous Bill

[YT2095]

there will be less water exiting (and thus entering) when you plug your TV in than the was before you did it.

 

there`s no puzzel

[CPL.Luke]

the same amount of mass has to exit the tube, but it would have to do so at a lower velocity (of course its pressure would increase to keep the mass flow constant)

 

the key in the problem is that the turbine isn't drawing any power until you plug the tv into it, so the water doesn't lose any energy into it (at the point where you say the amount of water exiting the turbine has the same velocity and flow rate as the water entering). But then you plug in your TV and that starts drawing juice, so the water slows down a bit.

[wpenrose]

Here's a puzzler for you. ...But the water entering the turbines is the same mass and velocity as the water exiting the turbines. So when you plug your TV into the turbine and it lights up, where does the energy come from?

 

The answer is that the potential energy difference due to the elevated water source is turned into a pressure difference before and after the turbine. The pressure drop across the turbine is the force, and the transit through the turbine is the displacement. Force x displacement = energy.

 

Turning your TV on draws current, and the turbine requires more force to turn. The slower flow allows the pressure difference to increase.

 

Dangerous Bill

[Harvey13]

Einstein's relativity tells us that an accelerated body gains mass, the extra mass being that of the KE; it has been verified countless times with accelerators. This theory would be problematic if we applied it to gravitational acceleration. What did Einstein mean by 'the equivalence principle'?

 

'Gravitional Fields' have the property of converting particle rest mass into KE mass so that a falling body does not change its total mass as seen in an accelerator. Hence: "A falling stone gathers no mass". Nigel Calder expressed the same idea in his book "Einstein's Universe" in Chapter 7: Shells of Time: "As no force acts on the apple, it cannot gain or lose energy".

 

There are no freebies in the energy game - with gravity (a conservative force) you add rest mass (most refer to this as potential energy) to the particle by raising it and you get it back when it falls. If we knew how to make the rest mass of a particle propel itself (gravity does just that) and then slow down withot ANY loss then we might almost have perpetual motion!

[D H]

Einstein's relativity tells us that an accelerated body gains mass, the extra mass being that of the KE; it has been verified countless times with accelerators. This theory would be problematic if we applied it to gravitational acceleration. What did Einstein mean by 'the equivalence principle'?

 

Relatively old threads should not be necromanced.

 

That said, it appears you are confusing rest mass, which is invariant, and relativistic mass, which is now widely viewed as unnecessary (it is tautologically defined by energy) and out-dated.

 

'Gravitional Fields' have the property of converting particle rest mass into KE mass so that a falling body does not change its total mass as seen in an accelerator.

This is completely wrong.

 

Nigel Calder expressed the same idea in his book "Einstein's Universe" in Chapter 7: Shells of Time: "As no force acts on the apple, it cannot gain or lose energy".

Step back and look at what happens classically, where gravitation is viewed as a force. The apple does not change energy in classical mechanics, either. Instead, what happens is that potential energy is transformed to kinetic energy. There is no change in the total energy, and no change in mass. The picture is a bit more complex in general relativity. There is a very slight change in mass due to orbital motion, but this change does not match the large change in classical (non general relativistic) kinetic energy when something falls a significant distance.

[Harvey13]

DH PHYSICS EXPERT, I worry about your use of 'necromanced'. According to my dictionary, magicians practise necromancy, which is the pretended art of revealing the future by communicating with the dead.

 

'Extra mass' is the relativistic mass and since E = mc^2, I see no reason why energy 'outdates' mass.

 

My red statement is in agreement with Nigel Calder's remarks. Perhaps a read of his excellent book would modify your misunderstandings.

 

Have you read that Einstein claimed that a rest mass on the surface of a gravitating body is less than it would be out in 'flat space'? He thought rest mass was variable.

 

I have not the foggiest idea of the meaning of your last sentence.

 

PHYSICS EXPERT, you have put out 643 postings since March 2006 (about 1 every 30 hours) and I suspect that you are neglecting to read some learned physics books.

Edited June 22, 2008 by Harvey13
multiple post merged

[Sayonara]

DH PHYSICS EXPERT, I worry about your use of 'necromanced'. According to my dictionary, magicians practise necromancy, which is the pretended art of revealing the future by communicating with the dead.

Then your dictionary does not account for the specialised vocabulary which is employed by sites such as this. That is not so much of a surprise, seeing as the web changes faster than dictionaries can be revised.

 

My red statement is in agreement with Nigel Calder's remarks. Perhaps a read of his excellent book would modify your misunderstandings.

This is an Appeal to Authority. Please avoid arguing by means of logical fallacies.

 

PHYSICS EXPERT, you have put out 643 postings since March 2006 (about 1 every 30 hours) and I suspect that you are neglecting to read some learned physics books.

Immaterial, and could be interpreted as flaming.

 

Since you enjoy sharing reading recommendations, perhaps you will take your own advice and peruse our rules and etiquette guide.

[D H]

DH PHYSICS EXPERT, I worry about your use of 'necromanced'. According to my dictionary, magicians practise necromancy, which is the pretended art of revealing the future by communicating with the dead.

 

I was talking about thread necromancy.

 

'Extra mass' is the relativistic mass and since E = mc^2, I see no reason why energy 'outdates' mass.

When used in the context of relativistic mass, the equation [math]E=mc^2[/math] is tautological. It defines relativistic mass. If you know the energy (a more useful concept), the relativistic mass is a given. The modern version of the equation is [math]E^2 = (mc^2)^2 + (pc)^2[/math] where [math]m[/math] is the invariant or rest mass and [math]p[/math] is the linear momentum.

 

In general relativity, a particle following a geodesic has a zero 4-acceleration. In other words, a free-falling object is not accelerating in general relativity. You are mixing concepts from classical non-relativistic mechanics and concepts from general relativity. Doing so is a bad idea.

[calbiterol]

So that people know what DH is talking about, I made reference to generating electricity by dropping rubbish down a shaft. I actually think I already mentioned this somewhere on the forum, but it's been so long since I was active here that I don't really remember!

 

EDIT: Oh jeez, didn't realize the rest of this thread was so old. I thought I remembered something like it...

Scratch that, reverse it. I'll remove myself from what appears to be a buddingly unproductive argument.

 

Cheers!

Edited June 23, 2008 by calbiterol

[D H]

Three problems:

1. You would have to dig the shaft first, and doing so would require energy to break the rock that occupies the space where the shaft will be into little pieces and energy to lift the little pieces of rock out of the shaft. That is a *lot* more energy than could be recovered from dropping stuff down the shaft.
    
    
   
2. How are you going to recover the energy?
    
    
   
3. The shaft will soon be filled with trash. What do you do then?

[padren]

What about launching objects out of and into gravitational fields?

This has bothered me for a long time and I may even have posted it here before. Suppose I take a very large mass and I use a certain amount of force to get it out of Earth's noticeable gravitational field, then aim it towards a much larger field like Jupiter (where I have previously placed a device that can harvest kinetic energy as objects fall). If you can put aside the difficulty in doing so, I get this large mass to land on my machine and I am able to contain all of its falling energy. Wouldn't I have more energy than I put in, since the weight of the object is greater in the larger field?

 

I think if you want to look at the "where would the energy come from?" question, it boils down to potential energy from "rocks lifted up" during the big bang and subsequent shaping of the local star system.

 

The "work" done in setting up the location of Earth and Jupiter was done a long time ago, and not by humans. It would be no different than gaining energy by tying a rope to a rock found at the top of a mountain and having it unwind from the axle of a generator.

 

 

The closest we have to pure "gravitational power generation" would be tidal power plants, which only require solar energy to keep the water from freezing, but not move it around. (The moon does that.)

 

Technically, (this is my assumption, not a proof) the resistance the water going through the turbines causes a slight mass of water to slightly "lag" behind the moon instead of being pulled directly up towards it, (just as friction resistance in the open ocean does to a lesser degree but on a larger scale) which causes the "center of mass" (Earth) that the moon is pulled towards to always be a bit lopsided and behind the Moon's orbit instead of directly below the moon - which in very small increments causes the moon to slow down and possibly crash into the earth one day.

 

Though, I think I recall the moon has a velocity that is actually causing it to get further away, and this "tidal drag" isn't enough to decelerate it enough to ever crash into the Earth.

 

I am not 100% sure, but I am pretty sure that is why a tidal power plant isn't considered a perpetual motion machine - the energy gained increases tidal drag, but due to the sheer amount of potential energy in the moon, the impact hasn't been notable even over billions of years.

[brian334]

Use KE and PE. At my website there is a description of a machine that uses both PE and KE to convert energy.

Edited September 14, 2008 by Cap'n Refsmmat
removed link

[Mr Skeptic]

Use the excess (ie, all of it) electrochemical energy in the brains of the people who don't understand how gravity works?

[drew]

i thought i saw something that was a working generator that runs only on gravitational force but im guessing it doesnt work because we are not using them. anyway i think i know how to make a gravity run motor that kind of uses a loophole to get around that work = distance/ power or whatever it is

[Klaynos]

i thought i saw something that was a working generator that runs only on gravitational force but im guessing it doesnt work because we are not using them. anyway i think i know how to make a gravity run motor that kind of uses a loophole to get around that work = distance/ power or whatever it is

 

Would you mind sharing what this wondrous loophole is?

[Sisyphus]

but im guessing it doesnt work because we are not using them.

 

It's amazing how many people whose minds this thought never crosses.

[pioneer]

Hydroelectric, such as dams, already use gravity as an energy source; water falling to lower potential. Along that theme, if we could trap rain water at elevation (mountains), we could use this solar induced gravitational energy as a renewable energy supply.

 

Approximately 505,000 km3 (121,000 cu mi) of water fall as precipitation each year

.

[toastywombel]

Hydroelectric, such as dams, already use gravity as an energy source; water falling to lower potential. Along that theme, if we could trap rain water at elevation (mountains), we could use this solar induced gravitational energy as a renewable energy supply.

 

.

 

I think this is a really novel idea.

[eva]

My idea was actually something along the lines of having some sort of generator that created energy while people walked over it, or something. Maybe build a city over it. I don't know how feasible this is, though.

 

Hey dude, you can. Where I work, there is an environment exhibition and they've got one with a portion of a dance floor that absorbs energy with springs. They use that energy to play music and use the lights.

[Moontanman]

Hydroelectric, such as dams, already use gravity as an energy source; water falling to lower potential. Along that theme, if we could trap rain water at elevation (mountains), we could use this solar induced gravitational energy as a renewable energy supply.

 

.

 

Hydroelectric has lots of environmental problems, from release of greenhouse gasses to environmental disruption. Most environmentalists are looking to decrease our use of hydroelectric from damns.