Where does energy go in resisting gravity

siarad · Jun 12, 2006

Please don't think of practicalities as an engineer like me would but just scientifically as a principle. I seem to have a problem understanding gravity but don't quite know what it is. An aircraft needs continuously to fight gravity simply cruising at a fixed height, where does this energy go. Don't know the calculation. If I drive my car it seems to store energy internally as inertia & return it as heat or for green use charge a battery or flywheel. If I walk up a hill carrying a bucket of water I get hot but the water cools, if I understand Joule correctly. Returning I still get hot but the water warms to its original temperature from where? Gravity is a constant, G, so energy can't be added or subtracted, or can it, so where does this energy in the water go to be so readily returned & seemingly tied to gravity in some way. Is gravity peculiar, in the same way as em waves, by being constant but able to store energy or does the energy go somewhere else? Sorry if this seems: silly worth thinking about better still has an answer.

enigma10 · Jun 12, 2006

You need to carefully identify all forces involved in each of your examples. I can offer a hint to some... Friction. <div class="Discussion_UserSignature"> "An organism at war with itself is a doomed organism." - Carl Sagan </div>

siarad · Jun 12, 2006

Well that's an engineers answer & is an irreclaimable energy. I speak of the reclaimable form but don't know how to reclaim the energy needed to hold the aircraft up but seemingly it's gone to the same place so ought to be available <img src="/images/icons/smile.gif" />

why06 · Jun 12, 2006

you do not realize..... There is another fight going on. One more powerful than all the energy generated in the world by any human means. On the sub-atomic level two elemenrty forces are facing of against each other.... The only thing that keeps earth and ererything else from collapsing due to gravity is a resistance called atomic energy. If electric energy - you know those buzzing electron were to be removed from all atoms the eathr would collapse. -THANK GOODNESS FOR ELECTRO-MaGNETICS <div class="Discussion_UserSignature"> <div>________________________________________ </div><div><ul><li>your move...</li></ul></div> </div>

harmonicaman · Jun 12, 2006

Einstein and E=mc2 changed the way we think of gravity. Gravity is merely the manifestation of time ("c") and the expansion of space curving around the static mass and energy ("m" and "E") in the universe. There is a conflict in the universe between the unchanging "m" and "E", (Law of Conservation of Mass-Energy) and the infinitely expanding "c". Since "c" cannot expand in the presence of the unchanging "m" and "E", it is forced into a curved path and must eddy around the "m". Since this curved path is longer than the straight path, it takes "c" a bit longer to expand around the "m" and "E" and we experience this phenomenon as gravity! Einstein defined gravity not as a force, but as an expression of the curvature of space and time itself. Note that inside of a black hole, the "m" and "E" becomes so compacted that "c" must infinitely curve around this solid and unchanging mass -- time comes to a standstill and space cannot expand; gravity too becomes infinite! The conflict between the "m" and "E" and the "c" in the universe has been going on since the big bang event; the "c" has had to curve around "m" and "E" since time began and this is all that gravity is; it isn't a force requiring a transfer of "E", it's just "c" curving around "m" and "E".

michaelmozina · Jun 12, 2006

Your questions are a bit unusual, but I'll try to answer them as best as I can. <blockquote>In reply to:<hr />Please don't think of practicalities as an engineer like me would but just scientifically as a principle. I seem to have a problem understanding gravity but don't quite know what it is.<hr /></blockquote> Welcome to life. Most people experience gravity everyday, but science isn't even sure what causes it yet. <img src="/images/icons/smile.gif" /> Most likely it's an electromagnetic "force" of some sort. <blockquote>In reply to:<hr />An aircraft needs continuously to fight gravity simply cruising at a fixed height, where does this energy go. Don't know the calculation.<hr /></blockquote> There is a slight problem here with nature of your question. Aircraft tend to to require forward momentum to create lift on the wing as the air rushes over the wing. As others have pointed out, there is friction involved in this process that must also be overcome during flight. The power that used by an airplane to stay aloft is typically far and away greater than the energy that is necessarily simply to overcome gravity. <blockquote>In reply to:<hr />If I drive my car it seems to store energy internally as inertia & return it as heat or for green use charge a battery or flywheel.<hr /></blockquote> That is actually a better example, since the flywheel stores energy as kinetic energy that can be converted into other forms of energy. When we apply "work" to overcome gravity, we are essentially storing this energy into potential energy which can later be converted back into kinetic energy if we let the object fall back to earth. A good example of this is a pendulum. You can watch it swing back and forth converting kinetic energy into potential energy and back again. Eventually friction from the air and in th <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

alek_a · Jun 12, 2006

The airplane thing... The plane moves through a fluid (air) and encounters resistance. That is where you must do work to keep the plane moving. And that is where the energy of the engines goes: in friction. If there was no friction with air, the plane could have glided forever with just one push. So, the glider planes, that have little friction, can stay in the air (fighting gravity) with low speeds (having large wings=lift surface) far longer than a 1 Mach jet would do with the same energy input (the energy required to climb the glider in the air in our case). The eneregy from the engine in you car is almost exclusively used to fight friction in the wheel bearings and with the air. And a small part (on the average) is used to accalarate (increase the car's speed and thus give it kinetic energy). When you decelerate (hit the brakes) that kinetic energy transformes into heat in the brakes (thats why you can see them getting red-hot before curves on the road in racing cars at night when the driver breaks).

toothferry · Jun 12, 2006

An aircraft needs continuously to fight gravity simply cruising at a fixed height, where does this energy go. Where does the energy go? It's always spent accelerating through space in a direction opposite to the ground. Think of space flowing towards the ground at the speed of Earth's gravity. All the air molecules, our atmosphere, get caught next to the ground simply because there is no where else for it to go since the Earth's Mass is blocking all other masses from staying in the same fixed X,Y,Z point in space, which a body cares to do. Space should be thought of as a static non moving dimensional plane of the universe. When masses block other masses from staying in their true spatial plane we describe that blockage, and the relative closer of distance between those two apparent mass dimensions ever shrinking, as gravity. Space isn't really acceleratingtowards the Earth at the "speed of gravity", but rather space is constantly static everywhere with an occasional large "mass", which always exist in 3 dimensions (or 4 if you include time), acting as a barrier, or a force field sort of, blocking other objects of mass from maintaining their same X,y,Z point in "space. The dimensions are bent by large masses, so to speak. When the airplane stays a constant altitude its spending lots of energy accelerating "through space". The plane stays at the same altitude because those static space dimensions are bent into the large mass. (Earth). Now, envision a huge bubble of atmosphere in outer space, no planet, in which your airplane can fly around in (because it has lots of oxygen there). There is no gravity, no up no down, your plane will be flying in loops else you will have to apply down elevators to keep it going "straight", to counter the opposite pull of the airfoil. No energy is required to "fight gravity", that is to accelerate through space in a d

siarad · Jun 13, 2006

Thanks guys you've all given thought to answers but have tended to answer as engineers by bringing up friction which is wastage not storage. Because I don't know quite what bugs me about gravity I gave some examples to hopefully get the idea over rather than to be answered. Changing from potential energy to kinetic energy can be accomplished by several ways, in a magnetic field say but also by gravity. I can see in the magnetic case the force field is distorted holding energy to be returned but with gravity the object itself changes. Joule on his honeymoon at Niagara falls measured the temperature differential of water finding it had increased at the bottom. This is the same water but has increased in energy by work done, just like stirring does, but from whence comes this energy. As I pointed out gravity, G, is a constant so can't have given up the energy unless it's peculiar like em waves i.e. gravity is in-consumable. Not a lot of time so I'll have to think more on your answers later.

enigma10 · Jun 13, 2006

Friction, though often used in engineering equations, is not to be confused as being exclusive to such boundries. With that in mind, to further discuss what elements of gravity you seek elaboration over, please define further which theory you are most comfortable with. http://en.wikipedia.org/wiki/Gravity <div class="Discussion_UserSignature"> "An organism at war with itself is a doomed organism." - Carl Sagan </div>

observer7 · Jun 13, 2006

You seem to be confusing "G" which is the gravitation constant and "the force of gravity". Gravity is not "constant" by any means. The gravitational force feels different on the surface of the Earth, surface of the Moon, at the orbit of Pluto, etc. "G", the gravitational constant shows how this force varies depending on the masses and distances involved. I too, am bothered by gravity. Mostly because although we can describe its effect, no one seems to be able to manipulate it like we can with the electromagnetic force. I sometimes think this is why it's proving so hard to unite gravity with the rest of the forces of nature. <div class="Discussion_UserSignature"> "Time exists so that everything doesn't happen at once" Albert Einstein </div>

michaelmozina · Jun 13, 2006

Any heat generated in the water at the bottom of the falls is likely due to friction between the water molecules as potential energy (at the top of the falls) is converted into kinetic energy (during the fall) and then into heat (at the bottom). Again, all energy was conserved. The water had potential energy at the top which was converted to heat at the bottom. Gravity may be thought of as "consumable" in so far as it is possible to break down atoms into other, smaller forms of 'energy' like photons and neutrinos. A nuclear weapon converts mass into energy for instance. It is possible however that this process simply moves mass around, and gravity itself (related to smaller particles of mass) is preserved throughout the process. You might try envisioning gravity as potential energy if that helps. <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

siarad · Jun 15, 2006

I didn't say gravity is constant but a constant. You're talking of g not G. g varies due to size & density but G is a constant. If the earth turned into a black hole the same gravity would have a greater effect simply coz you'd get closer to it <img src="/images/icons/smile.gif" />

siarad · Jun 15, 2006

Ah so! I kinda see that as water breaks up during a fall. Yes seems a good explanation thanks <img src="/images/icons/smile.gif" /> sniff sniff why can't I get a lightbulb in text <img src="/images/icons/frown.gif" />

siarad · Jun 16, 2006

Thinking more on this whence cometh potential energy? As gravity can't give energy then potential energy must be somewhere. At least some water has come from space, apparently, so has not been 'given' potential energy by rising from Earth, but must contain it. Not being extant at the BB it has come from somewhere so is there a potential energy, P, constant like G & C. In the absence of gravity, potential energy like mass would be invisible so still seems tied to gravity & is not energy at all but still heats water <img src="/images/icons/rolleyes.gif" />

spacester · Jun 28, 2006

Gravity is an energy field. Potential Energy is zero in the absense of a gravity field. If one looks to the energy equation - aka the Vis-Viva equation - for insight, one sees that indeed the Potential Energy associated with a Gravity Field is negative. So, as you say, the Earth does not 'give' an object in its gravity field the energy; the energy seems to exist in the universe and the presence of the mass creates a field of energy which is 'negative'. I suppose the question then becomes a matter of determining the meaning of the word 'negative' in this context. Just my $0.02 <div class="Discussion_UserSignature"> </div>

siarad · Jun 30, 2006

I just wish I knew what I don't understand about gravity it really bugs me not being able to formulate a question so I thrash around. Oddly there's another topic about gravity waves where energy seems to be lost so there must be a metamorphosing of matter to gravity waves.

vandivx · Jun 30, 2006

<blockquote>In reply to:<hr />I too, am bothered by gravity. Mostly because although we can describe its effect, no one seems to be able to manipulate it like we can with the electromagnetic force. I sometimes think this is why it's proving so hard to unite gravity with the rest of the forces of nature.<hr /></blockquote> we can't do things with gravitational force that we do with electricity because it is different from electricity, simple as and that applies to second part, why it's proving so hard to unite those two, never mind rest of forces of nature. Gravity is simply different from other forces, it is sui generi (I think that's correct latin for 'its own thing' LOL). All those efforts of unification are putting horse behind cart since they try to put together something which they don't understand in the first place, there is no really deep understanding of gravitation and electromagnetism which may surprise many especially given what handle we have on electricity. Thing is that 'handle' is like monkey playing with modern technology, he can learn to manipulate it but won't understand what makes it work. Electric charge is a charge is a charge, that's most any physicist will be able to tell you, with gravitation there is even less insight. Unification then is blind striving in hopes it will click and voila, theory of everything is here through our trying to put it together this way and that way, only it doesn't seem to work that way. Unification is motivated by past successes that unified whole area of physics, like Maxwell's equations of electromagnetism, but one can't simply expect that past successes can be just analogously followed to get results. If physics were that simple, we would be finished with it and we wouldn't need any geniuses to do that. vanDivX <div class="Discussion_UserSignature"> </div>

siarad · Jul 1, 2006

Well it does seem gravity is a complete red herring, perhaps not even existing, or at least maybe it's a catalyst enabling mass to link to space & it's there we should look for the store of energy. If I carry a kg bottle of water to the top of Niagara, some 28m, then it's gained 280J of gravitational potential energy. If this energy came from my leg muscles how is it stored in the water or is the weakening of gravity the indicator oo er, this would mean infinite energy for any object way out in space <img src="/images/icons/rolleyes.gif" /> just too silly so it must store in the water how. If I drop this bottle over it heats by 280J how.

kmarinas86 · Jul 1, 2006

Well it does seem gravity is a complete red herring, perhaps not even existing, or at least maybe it's a catalyst enabling mass to link to space & it's there we should look for the store of energy. If I carry a kg bottle of water to the top of Niagara, some 28m, then it's gained 280J of gravitational potential energy. If this energy came from my leg muscles how is it stored in the water or is the weakening of gravity the indicator oo er, this would mean infinite energy for any object way out in space just too silly so it must store in the water how. If I drop this bottle over it heats by 280J how. OMG

Saiph · Jul 1, 2006

siarad, let me ask you this: You have a rubber band, which you stretch taunt, then use to launch a pencil across the room. Where does the rubber band get the energy? Where is the energy before you've stretched it? After stretching but before you launched the pencil? In your waterfall example, the water gained energy because you expended the energy stored in your body (within chemical bonds of molecules) to lift it up. You too gained energy (since you went up with the water). When you stopped at the top that energy was "potential" energy, as it does not influence the current state of the system, but only what the system "can" do. When you drop it, the energy stored by moving the water higher above the ground is returned as kinetic energy. This causes the bottle to move, and move faster as more potential energy turns to kinetic. Upon impact, the organized motion of the water is disrupted into a random motion, and this random motion of molecules is what is measured as a temperature. A temperature is only a gauge of the average kinetic energy of a material stored as random motion. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

siarad · Jul 2, 2006

When I pull an elastic band I'm in contact with it & the energy is returned. Carrying the bottle of water doesn't impart energy but adds potential energy at the expense of kinetic energy surely, by what means does gravity accomplish this. The water heats, this is real energy from where. The water must have changed under the influence of gravity by what mechanism. Yes I can shake the water to heat it but it's my energy, the fallen water can't consume gravity so where does it's energy come from. If it's from me climbing with it how do I impart this through the bottle, it seems to be with the aid of gravity, by what mechanism. This seems to break the potential/kinetic ratio constancy or am I missing something. Can I measure any difference between the water at top or bottom given resting time, I'm guessing only that it's no but the answer seems to be yes, so I'm stuck with gravity being in-consumable but heat energy has appeared. The problem with this topic is my inability to know what I don't know about gravity so I'm tossing things around hoping for the 'that's it' moment.

kmarinas86 · Jul 2, 2006

When I pull an elastic band I'm in contact with it & the energy is returned. Work was performed on the rubber band. Both your muscles and the rubber band heated. Carrying the bottle of water doesn't impart energy but adds potential energy at the expense of kinetic energy surely Kinetic energy is relative because velocity is relative. When you stop moving, what causes that? A change in potential energy? Nope. Remember that velocity depends on both magnitude and direction. , by what means does gravity accomplish this. The water heats, this is real energy from where. The water must have changed under the influence of gravity by what mechanism. Yes I can shake the water to heat it but it's my energy, the fallen water can't consume gravity so where does it's energy come from. For the bottle water case: Gravitational "binding" energy = GMm/r http://www.google.com/search?q="gravitational+binding+energy" In effect, the "binding energy" is inversely proportional to the distance between M and m. If it's from me climbing with it how do I impart this through the bottle, it seems to be with the aid of gravity, by what mechanism. Gravity doesn't aid it. The friction beween your feet and the mountain provide the thrust you need to carry the water with you. The chemical energy originally comes from photosynthesis. The chemical energy you get may be used to perform different tasks, including thinking about what your going to do with the water as well as taking it up them mountain with your muscles. This seems to break the potential/kinetic ratio constancy or am I missing something.

Saiph · Jul 2, 2006

<blockquote>In reply to:<hr /> When I pull an elastic band I'm in contact with it & the energy is returned. <hr /></blockquote> But where in the rubber band is the energy stored? Lifting the bottle requires exerting a force (your lifting) over a distance (height lifted) which is work which is energy. As mentioned gravitational energy is binding energy, it's the same thing as the binding energy between electrons and protons, which, btw, is where the energy in a rubber band is stored. When you stretch a rubber band, you move the molecules further apart, even stretching individual molecules, away from an equilibrium position. By doing so the energy you used to stretch the rubber band is "stored" in the new positions of the molecules. When no outside force interfers, they revert to their old positions (as that's the direction the existing forces act upon them) and "release" the energy. So, here's the force picture for gravity: Gravity exerts a force downward, which will accelerate an object downward, unless opposed by another force. When the object is on the ground, the ground exerts a force upwards, countering gravity (that is, if the object is just sitting there). When you lift an object, you exert more force than gravity, and create a net upward force. Now, you exert this force over a distance, which is doing work, supplying energy. When you stop lifting the object, you are only supplying enough force to counter gravity. You are no longer doing any work (while applying a force you aren't doing so over any distance) you are no longer supplying any more energy to the bottle earth system. Now, when you let go, there is no opposing force, and gravity pulls the bottle down, exerting it's gravitational force over a distance (the same distance you raised the object)...and so it does work. The work it does, is the same amount of work you did, a <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

siarad · Jul 3, 2006

Thanks Saiph & kmarinas86 I've used these things all my working life but now retired am trying to understand why. I do understand what is being said, it's not my problem but it's all I can think of as a question. Instead of my aeroplane above take a hovering helicopter, the same thing, it's doing no work but burning energy. Well this resultant heat isn't anti-gravity but why is it required. A fact of life, I hear, something I don't like so maybe I'm asking the impossible. The helicopter sat on the ground uses no energy, is the ground supplying it, well I guess not. So the air or space doesn't have sufficient strength to counteract gravity. However gravity is reputedly a field distortion of space which does have sufficient strength, now that doesn't make sense <img src="/images/icons/rolleyes.gif" /> If gravity finds this strength of space why can't we & use it. Is what we call gravity a reaction of space & we've never found the originating force. Yes rambling but what else can I do the get an answer to an unknown question <img src="/images/icons/smile.gif" />

Where does energy go in resisting gravity

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