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Blah, blah, blah ... ----- In the one case there is an increase in gravitational potential energy, and in the other case there is not. And so, for energy to be conserved, there must be a decrease in another form of energy when the airfoil rises that does not occur when the airfoil does not. What is it? ? I don’t think you can answer this question. ? .

I have not spent forty years balancing things but I do speak English. I know the meaning of the word “balance.” And I know what the concept of “balance” means in the context of conservation of energy. I thought (mistakenly) that you were saying that when a less dense object rises in a more dense fluid that there is an increase in gravitational potential energy. There is not. There is an increase in the gravitational potential energy of the rising object, but there is a greater decrease in the gravitational potential energy of the falling fluid. And so, there is a decrease in gravitational potential energy. And the “balance” is that there is an equal increase in kinetic energy in the form of the rising solid and falling fluid (assuming no loses to friction). In your “balance” there are two energy increases and no energy decreases. Huh? You left out the decrease in the gravitational potential energy of the fluid in your “energy balance.” How can you now say I’m the one who is missing the important contributors? If the fluid is a liquid and if the container of fluid is both in a gravitational field and in a vacuum, then the risen solid will bob forever (in a frictionless world). No. There is no friction in this thought experiment. And I’m not going to go down another tangent with you (where, in all likelihood, I’ll make another mistake. I make a lot of them. And I don’t mind admitting when I do.) I suspect you can’t answer the simple question posed in post #46. And I suspect what you are doing is bringing up every possible tangential concept in order to muddy the waters and make it seems as if this question is so complicated that it is beyond any of us ordinary folk’s ability to address and so we should just leave it alone and walk away. One way to “resolve” an issue is to answer the question, and another way to “resolve” an issue is to make it go away. If I’m wrong about your motives, I apologize. And you can easily prove I’m wrong about your motives by simply answering the question. ----- In the one case there is an increase in gravitational potential energy, and in the other case there is not. And so, for energy to be conserved, there must be a decrease in another form of energy when the airfoil rises that does not occur when the airfoil does not. What is it? (The only energy change option, I can see, is a decrease in the velocity of the wind (and so a decrease in kinetic energy) when the airfoil rises. And the only mechanical reason I can see for this is an increase in drag when the airfoil rises. But, there is a problem with this logic when it comes to differently shaped airfoils of equal masses and volumes. And, so, this is where I am stuck. This is where, for me, the conservation of energy analysis remains unresolved.) ?

Huh? I said: Friction was not what keeps the airfoil(s) in the thought experiment in post #46 in place. If the one airfoil is kept in place horizontally but is allowed to move vertically, then it is not friction that keeps it in place. Friction would work in both directions. (Unless you are proposing that there is horizontal friction and not vertical friction. Which seems weird. And is unnecessary. The airfoil, it can be stipulated, in in a frictionless track that allows it to move vertically and not horizontally.) And, I said: In your thought experiment in post #62 where the rising submerged object eventually comes to a stop, for this to happen there must be friction. I don’t understand your point. --- Okay. Perhaps I missed your point. In post #55 you write: “If the (bouyancy) force leads to movement of the object then it will accelerate the object, imparting the kinetic energy of movement to that object. In addition, once the object has been moved upwards some distance (any distance however small) then it also imparts gravitational potential energy. All this is fine and dandy and leads to the following energy balance. As soon as a net bouyancy force exists (however small) it accelerates the object upwards (however slowly), thus imparting kinetic and potential energy to the object as noted above.” (bold added) Okay. If you are saying when object rises in a fluid, that for that object in and of itself there is an increase in gravitational potential energy, while, depending on whether the fluid the object displaces is of a greater or lesser density, then, overall there will be an increase or a decrease in gravitational potential energy then I agree with you. Where I then have a problem is where you say: “All this is fine and dandy and leads to the following energy balance. As soon as a net bouyancy force exists (however small) it accelerates the object upwards (however slowly), thus imparting kinetic and potential energy to the object as noted above.” If I understand you now correctly (as spelled out in the previous piece of logic), then, yes, your second sentence above makes perfect sense. But the prior sentence then does not. If I now understand you correctly, you are not “balancing” out energies in the “following” sentence. You are saying, in this second sentence, when a less dense object rises in a more dense fluid that for that object in and of itself (and without any reference to the rest of the system) there is both an increase in kinetic energy and an increase in gravitational potential energy. There is no reference to the greater amount of mass of fluid that “falls” or “descends” or is “displaced downwards.” There is no “balancing” of the increase in kinetic and gravitational potential energies of the solid in and of itself with the increase in kinetic energy of the descending fluid and the decrease in gravitational potential energy of the descending fluid which must be for an “energy balance.” Saying there are two increases in energy with the rising submerged solid is not an “energy balance.” When I read this I assumed since this was supposed to be an “energy balance” that you were attempting to balance the energies, and the only “gravitational potential energy” change in this system that leads to a “balance” is the decrease in gravitational potential energy of the descending fluid (which apparently, if I now understand you correctly, you did not include but rather where just listing the two increases with the object). And so, if I now understand you correctly, this was a mistaken reading of what you wrote on my part. (If so, apologies.) So, ... Either I misunderstood you and thought you were trying to balance the increases with the decreases in energy, when in fact you were just listing the energy increases for the submerged solid and that alone, in which case your statement “... and leads to the following energy balance” is flat out incorrect Or you were claiming to balance out the energies, and so your statement “... and leads to the following energy balance” is genuine but in the “following” sentence you fail to balance anything out and just list the two energy increases for one part of the system. And, so, yes, perhaps I missed your point. And if I did, I apologize. And, if so, now to you: where is the “balance” in the “following”? And if there is none, then what is your point? --- In the rising case it does. --- To J.C.MacSwell: I’m still thinking about the efficiency angle. I’ve never thought about it from this perspective before. My initial gut feeling is that this isn’t going to work. But I need to think it through and will.

A body will continue in motion (even if that motion is redirected in an elastic collision) unless something stops that motion. When the submerged solid rises (and eventually reaches the top of the fluid) and when the fluid is displaced downwards, they will both will continue moving unless something else stops them. In a frictionless world (as it is so been stipulated here for the purposes of analysis) when the submerged solid reaches the top of the container of fluid it will (due to the fact it is upward vertical motion) move up beyond its preferred position (lowest energy state) at the top of the container of fluid and then it will fall back down, below its preferred energy state (since it now has downward vertical motion), and it will continue to bob up and down like this forever unless something else (such as friction) stops it. It retains all of the kinetic energy (in oscillation with potential energy as it bobs above and then below its preferred position and comes to periodic and temporary stops) it gained from the equal loss in gravitational potential energy. In your example, where the rising solid and displaced fluid come to a stop, it is friction that must bring them to a stop. And when friction decreases kinetic energy there is an equal increase in thermal energy. Energy is conserved. To recap (in your friction filled example which is not the thought experiment presented here): The less dense object rises and the move dense fluid is displaced downwards. This is a decrease in gravitational potential energy. The submerged solid and the displaced fluid are set into motion. This is an equal increase in kinetic energy. The solid and the fluid come to a stop. This is a decrease in kinetic energy. It is friction that brings them to a stop. There is an equal increase in thermal energy. Energy is conserved. It is all very simple and all very clear. If I’m standing in my backyard and I throw a ball up in the air, the ball will rise and it will slow down as it rises. The more dense ball displaces the less dense fluid downwards. There is an increase in gravitational potential energy and a decrease in kinetic energy. In this case the rising object gains gravitational potential energy. There is no lack of “acceptance” of this on my part. However, if the rising object is less dense and if the fluid displaced downwards is more dense then there is rather an acceleration and a gain in kinetic energy and a loss in gravitational potential energy. So, no, I am not willing to “accept” that in the case of a solid rising in a fluid due to the upward buoyant force on it that there is a gain in gravitational potential energy. This almost seems axiomatic. I did read both lines. And I only quoted the second because the first sentence is right (there will be an increase in kinetic energy) and the second one is wrong (there will not be an increase in gravitational potential energy). If what you are saying (in the two lines) is true (which is it not) then you are saying when a submerged solid rises in a container of fluid due to “buoyant potential energy” then energy is not conserved. I’m not saying this, you essentially are. You are saying there is both an increase in kinetic energy and an increase in gravitational potential energy. And so the one does not offset the other. If you are right (which you are not) then energy is not conserved. No? If we are still in disagreement about this I would be willing to try to clarify it further. But, again, this is such basic physics and such basic logic that everything I have said in this reply almost seems axiomatic. --- Does anyone have any ideas on how energy is conserved when the airfoil rises in the thought experiment in post #46 (or as modified and improved in post #54)?

Huh?

Ouch.

Okay. Your post #49 appears, to me, to be an analysis of the situation. And so you seemed, to me, to reach a conclusion and not merely asserting conservation of energy. This is a Science forum where the Law of Physics are, of course, assumed to be true. And so “energy is conserved” can be simply be asserted. However, if one desires to understand how energy is conserved in a given situation (as I do) then analysis is required. --- Yes. In this thought experiment (post #46) the “airfoil” can be in any fluid. It can be in a gas or a liquid. The logic, and the issue, remain the same. It should be assumed, for the ease of analysis, that the fluid is incompressible. If the “airfoil” is neutrally buoyant (the same density as the fluid it displaces) then, in the end, in the rising case there in an increase in kinetic energy (in the form of the rising “airfoil” and the fluid displaced downwards) that does not occur in the non-rising case, and so there must be a decrease in another form of energy in the rising case that does not occur in the non-rising case. The issue essentially remains the same. (And this simplifies things in that the vertical kinetic energy is no longer then later transformed into gravitational potential energy.) And, yes, it should be assumed this all occurs in a hypothetical frictionless world. Thank you for the improvements (simplifications) to this thought experiment. If I read J.C.MacSwell’s post correctly, he says that the velocity of the wind will decrease more in the non-rising case than in the rising case (which means the velocity of the wind does not offset the difference in the kinetic energies of the rising versus non-rising “airfoils” but only adds further to the imbalance in energy conservation between the two cases) ... but ... then he suggests (somehow) that this does balance things out. --- When I throw a ball is thrown up into the air how fast the ball is traveling when it leaves my hand and how quickly the ball decelerates and how far the ball travels do not need to be included to analyze how energy is conserved in this situation. To include these values is fine, but it is not necessary, and they can potentially (if one was so inclined) be used as a distraction from the actual issue. Energy is conserved because the decrease in kinetic energy of the rising ball is matched by an equal increase in gravitational potential energy (plus the increase in the kinetic energy of the displaced air plus any increase in thermal energy). Energy is conserved and this is clear. And it is clear how energy is conserved. No numbers are needed for the how of it. When I drop a ball off of my roof the more dense ball falls and the less dense air is displaced upwards. There is an increase in kinetic energy and a decrease in gravitational potential energy. When a submerged solid in a container of fluid rises the less dense solid rises and the more dense fluid is displaced downwards. There is an increase in kinetic energy and a decrease in gravitational potential energy. It does not matter if the falling more dense material is a solid or a fluid and it does not matter if the rising less dense material is a solid or a fluid. In both cases there is an increase in kinetic energy and a decrease in gravitational potential energy. If you have a solid submerged in fluid and it is in free space far from any gravitational fields then there is no buoyant force on that solid. To get a buoyant force on a submerged object you need to be in a gravitational field. And to get “buoyant potential energy” where the overall upward force is greater than the overall downward force then you need to have a less dense object in a more dense fluid. This is a form of gravitational potential energy. No. It does not “impart” gravitational potential energy. It loses gravitational potential energy. No. If the one airfoil (as described in post #46) is able to move vertically but not horizontally then it is not friction that keeps it in place. It must be in some sort of track (a frictionless track it is now here so stipulated) that allows it to move vertically but keeps it in place horizontally. In the thought experiment in post #46, in the end, in the one case there is more gravitational potential energy than in the other. And so, for energy to be conserved, there needs to be a decrease in another form of energy in the rising case that does not occur in the non-rising case. What is it? Is it unknowable? The only energy change option I can see in the system is a decrease in the motion of the wind (and so a decrease in kinetic energy). And the only mechanical reason I can see for this happening is an increase in drag when the airfoil rises as opposed to when it is held in place. But there is a problem with this logic when it comes to differently shaped airfoils of equal masses and volumes. And (!) if J.C.MacSwell is right and the opposite is factually physically true (there is more drag when the airfoil is held in place than when it is allowed to rise) this only compounds the conservation of energy analysis problem. --- In a closed system, if there is an increase in one form of energy (such as gravitational potential energy), then there needs to be a decrease in another form of energy (such as kinetic energy) for energy to be conserved. If not the velocity of the wind, then what? ?

How far do I say (or show) the airfoils rise? And how fast do I say (or show) the airfoils rise? Huh? In the restatement of the issue (please see post #46 in this thread) the air moves horizontally and not the airfoil. There is no “thrust” or “power” moving the airfoil as part of the conservation of energy analysis of the issue in this form. If I understand you correctly, you are saying that when the airfoil is prevented from rising the velocity of the moving air decreases more and when the airfoil is allowed to rise the velocity of the moving air decreases less. Is that right? If, in the end, there is more kinetic energy in the case where there is also more gravitational potential energy and if, in the end, there is less kinetic energy in the case where there is also less gravitational potential energy (... if I understand you correctly ...) then how do you reach the conclusion that the conservation of energy analysis has been resolved and the energy in this scenario has been shown to be conserved? ?

Yep. The only energy change option possible in this scenario is the wind must be slower in the case where there is more gravitational potential energy in the end. And it’s not enough to just assert that the wind will be slower. There must be a mechanical reason why the wind is slower. And, so, the only option here is “there is more drag when the airfoil rises than when that same airfoil remains in place.” And this additional drag must slow the wind down by the precise amount so that the decrease in kinetic energy is exactly equal to the increase in gravitational potential energy (... for energy to be conserved). When I first reached this point in this analysis I thought I had resolved the conservation of energy analysis. But ... then I kept thinking and realized this can’t be right. If you have different airfoils all with the same mass and same volume, but with different shapes, then there must be the same amount of additional drag as each one rises since there is the same increase in gravitational potential energy as each one rises. Is there? When each differently shaped airfoil is held in place and the wind passes over them, given that they are each shaped differently, the odds are there will be different amounts of drag with each one. Now, when each of them rises, one, there needs to be an additional amount of drag to slow the wind down more and to offset the increase in gravitational potential energy and, two, this additional amount of drag must be the same for every airfoil of the same mass and volume regardless of its shape. But it stands to reason that if there is an additional drag when an airfoil rises that that amount of additional drag (and so the amount of slowing of the wind) will vary and depend on the shape of the airfoil. But this means (if there are different amounts of additional drag when the differently shaped airfoils of the same mass and volume rise) that the decrease in kinetic energy of the moving wind cannot be precisely equal to increase in gravitational potential energy for every differently shaped airfoil. And, so, energy could not be conserved in every differently shaped case due to this proposed additional, but varying, drag. No? If this thinking is right, then the conservation of energy analysis is still not yet resolved. ?

This new conversation between cxxLjevans, studiot, and MigL leads right back to my original issue with the conservation of energy analysis of an airfoil. I’ll try to present my problem again in light of this conversation and in a different way. If a solid is submerged in a more dense fluid then the force from the pressure pushing down on the top of the object plus the weight of the object will be less than the force from the pressure pushing up on the bottom of the object. This is energy. Energy is the ability to do work. This is gravitational potential energy. And if the solid is allowed to move then the less dense solid will rise and the more dense fluid will fall. There will be an increase in kinetic energy and an equal decrease in gravitational potential energy. --- If the air moves horizontally over and under a stationary airfoil, it moves more quickly over the top and less quickly under the bottom. Moving air along a solid means less pressure from the air on that solid; and the faster the air the lesser the pressure. So, the pressure from the air on the airfoil decreases and it decreases more on the top than on the bottom. It’s as if the airfoil has been moved into another fluid of greater density. (The denser the fluid the greater the pressure gradient.) Is this energy? It must be. Energy is the ability to do work. If the airfoil is free to rise, it will rise if the force from the pressure pushing down on the top of it plus its weight is less than the force from the pressure pushing up on the bottom of it. There will be an increase in kinetic energy (vertical motion). This increase in kinetic energy must come from some other form of energy. And it comes from (... I don’t know what else to call it ...) the “simulated gravitational potential energy” created by the different decreases in pressures on the airfoil from the moving air. And where does this energy (the “simulated gravitational potential energy”) come from? In order to get this energy (from the different decreases in pressures on the top and bottom of the airfoil) the air (or the airfoil) must be in horizontal motion. This motion is kinetic energy. And so, for energy to be conserved, there must be a slowing of this (a decrease in the velocity of the moving air and so a decrease in kinetic energy) to offset the increase in “simulated gravitational potential energy” (which then, in turn, becomes vertical kinetic energy, which then, in turn, becomes an increase in actual gravitational potential energy). And if this analysis is right, then energy is conserved. ----- Here is the issue. In the one case the wind blows and the airfoil is not allowed to rise, and in the other case the wind blows and the airfoil is allowed to rise. The blowing wind then passes on and the airfoils remain at whatever height they are at. So, in the end, the one airfoil is up in the air (fixed to a pole) while in the other case the other airfoil remains near the ground. In the one case there is more gravitational potential energy in the end and in the other case there is less gravitational potential energy in the end. And so in the one case there must be a decrease another form of energy that does not also occur in the other case. When the airfoil rises there must be a decrease in another form of energy that does not occur when the airfoil is prevented from rising. (As well as to also offset the increase in vertical kinetic energy of the rising airfoil and the vertical kinetic energy of the air displaced downwards.) The only energy change option in this system is the motion (the kinetic energy) of the wind. So, for energy to be conserved, when the airfoil rises there must be a decrease in the horizontal velocity of the wind (a decrease in kinetic energy) that does not occur when the airfoil remains in place near the ground. Is there? Why would there be a decrease in the horizontal motion of the moving air when the airfoil rises that does not occur when the airfoil remains in place? More drag? ?

What I should have written in my first post is this: “There is a decrease in chemical potential energy. There is an increase in thermal energy. There is an increase in energy in the form of demagnetization. There is a change in the amount of energy in the form of demagnetization versus magnetization. And there is a change in the amount of potential energy due to mutual attraction between the two magnets.” This way I could have avoided the discussion of whether magnetization or demagnetization is the higher energy state, while still noting the energy change, and moved on to the issue I’m having with too much potential energy found. ----- However, having said that, it’s interesting (in a sort of meta-analysis way) that if you type in “is magnetization the higher energy state” or “is demagnetization the higher energy state” into Google you don’t get, I find, a simple clear answer. (And, sadly, if you type in the latter now this forum discussion now is the first thing to come up.) Here is a link and a drawing that I came across that may be helpful to this discussion: http://www.irm.umn.edu/hg2m/hg2m_d/hg2m_d.html (A similar description can be found in Wikipedia: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&sqi=2&ved=0CCQQygQwAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FMagnetic_domain%23.22Magnetized.22_states&ei=CtLHVLywPIHsgwST8oKwBw&usg=AFQjCNF9pBJb-Cn32--VcvgwwFmMEzlwhg&sig2=ONWT3-k9bSJNrpwUATdS5Q&bvm=bv.84349003,d.aWw) The professor is positing that the preferred energy state for a ferromagnet is multi-domain rather than single domain (and the more domains the better). And the combined fields from the multi-domains tend to cancel one another out at a distance, and so when there are the maximum number of multi-domains possible the ferromagnet does not have much of an external magnetic field. To quote Wikipedia, the magnet has been “unmangetized.” This is different, however, from what I believe we have been discussing here. Randomization of the magnetic dipoles (which is what occurs upon reaching and exceeding a ferromagnet’s Curie temperature) is not the same as multi-domain magnetic alignment of the magnetic dipoles. John Cuthber, you wrote: “Domains form spontaneously, but bar magnets don't” And so, perhaps, you believe that multi-domain magnetic alignment of the magnetic dipoles is the lower energy state and a single domain bar ferromagnet is the higher energy state. ? (I do.) But this is not an issue here. Here we have a single domain bar ferromagnet that then becomes demagnetized (it becomes randomly magnetically aligned not turned into multiple lines of alignment). And if more and more domains of alignment is the lower and lower energy state, then it stands to reason that going in the opposite direction from a single domain alignment to randomization (no alignments) should be then the higher energy state. (Otherwise, when you have a single domain bar ferromagnet there would be the two competing tendencies to, one, increase the number of aligned domains and, two, move towards less alignment and to randomization. And this is a logical impossibility.) But ... again, again, again ... whether or not the magnetized state or the demagnetized state is higher, lower, or equal to one another is beyond the scope of the original issue in this thread. If the demagnetized state is the higher energy state, then there must be a decrease in thermal energy upon demagnetization. If the magnetized state is the higher energy state, then there must be an increase in thermal energy upon demagnetization. And if they are equal energy states, then there must be no change in thermal energy due to this upon demagnetization. But then, regardless of which of the three above conservation of energy options is true, the logic in the first post in this thread still leads to too much potential energy found. This side discussion has been interesting. And, thank you all, I am learning (whether you believe I am or not).

Thank you for the link, John Cuthber. Again, whether the magnetized state is a lower, higher or equal energy state to the demagnetized state is not what leads to the issue presented in the first post in this thread. I included it as a matter of housekeeping and in an attempt to include all of the changes. If magnetization is a higher energy state or an equal energy state to demagnetization, in the end, there is still too much potential energy found. However, having said that, the link you presented leading to “Magnet quench” occurs with superconducting electromagnets. And I’m sure there are both similarities and differences between an electromagnetic and a ferromagnet. In the article you linked to it reads “This [Magnetic quench] can occur because the field inside the magnet is too large, the rate of change of field is too large (causing eddy currents and resultant heating in the copper support matrix), or a combination of the two.” If you are suggesting that the same thing occurs with ferromagnets, I am at a lost for how “the field inside” a ferromagnet can be too large? Are you saying when a ferromagnetic is in its magnetized state that the field that comes from this can be “too large” for the magnet itself and thus can cause the ferromagnetic to undergo “magnetic quench” due to its own field being too strong? And are you saying that as a ferromagnetic is magnetized or demagnetized, and so there is a “rate of change” in the field, that something analogous to “heating the copper support matrix” occurs even though there is no “copper support matrix” with the ferromagnetic? And, finally, if there is a concentrated amount thermal energy around a ferromagnet putting it above its Curie temperature and then this thermal energy disperses and the ferromagnetic is cooled to below its Curie temperature and so then spontaneously magnetizes, are you saying that the amount of thermal energy within the system decreases? (This must be the case, if you are right and the magnetized state is a higher energy state than the demagnetized state, for energy to be conserved.) Does the spontaneous magnetization of a ferromagnetic also absorb heat? Again, whether or not the demagnetized state or the magnetized state is the greater, lesser, or equal state(s), is beyond the issue presented here. However, it is important to get all of the details (even the tangential details) right. So ... thank you for this discussion. Do you have any links (other than ones involving electromagnets) that support your position? Again, I am open to being corrected. ?

John Cuthber: The issue in my (rather lengthy) first post in this thread is too much potential energy found in the end. Whether or not the demagnetized state is a higher or lower or equal energy state to the magnetized state is tangential to the issue presented. But ... thank you for challenging me on this. I want to make sure everything is accurate (even if it is not essential to the core of the issue). I understand you disagree with me. Do you also disagree with imatfaal? “The parallel spin state of a ferromagnet is a lower energy configuration than the jumble of a non-magnet - it takes energy to make it lose its array of similar magnetic domains.” http://www.scienceforums.net/topic/87342-where-does-the-potential-energy-of-a-field-reside/?p=847543 And do you also disagree with MigL? “It takes a certain amount of energy to 'randomize' all the tiny magnetic domains in the single magnet.” http://www.scienceforums.net/topic/87489-a-magnet-is-demagnetized/?p=849512 If it takes energy to change a body from one state to another then that state it is changed into is the higher energy state. Please let me know if you still disagree with me, while not with your two colleagues, if you can find a way to distinguish my statement from theirs. ?

I made two bad typos in my original post. In a footnote I switched “increase” and “decrease” (although this doesn’t affect the overall statement of the issue) and in another sentence I left out the word “to” (the absence of which makes the sentence nonsensical). I should have written ... “(If the potential energy between them due to mutual attraction is positive then there needs to be an additional increase decrease in thermal energy, if the potential energy between them due to mutual attraction is negative then there needs to be an additional decrease increase in thermal energy, and if the amount of potential energy between them is 0 then there needs to be no change in the amount of thermal energy, to then offset the change (or no change) in the potential energy between them due to the loss of mutual attraction.)” And ... “When one of the magnets is demagnetized it is instantly cut off from the shared magnetic field and so whether the other magnet is demagnetized at the same time or whether it remains magnetized is immaterial to the demagnetized magnet (or magnets).” Apologies (... if anyone made it through my rather lengthy post).

It is. Actually, the problem is with too much potential energy found. Yes. I realize my first post in this thread is a long one. But there are three cases. The problem I'm having involves the third case. You and I agree about the first two cases.

A magnet is demagnetized. In a closed system there is a ferromagnet and two chemicals in a packet nearby. If the chemicals are exposed to one another thermal energy is generated. (There will be a decrease in chemical potential energy and an equal increase in thermal energy.) The increase in temperature will be enough to raise the ferromagnet above its Curie temperature. (There are no other strong magnetic fields nearby.) EN1 The chemicals are exposed to one another and the temperature increases. The ferromagnet becomes demagnetized. The demagnetized state is a higher energy state than the magnetized state. EN2 There is a decrease in chemical potential energy. There is an increase in thermal energy. And there is an increase in energy in the form of demagnetization. And so, for energy to be conserved, in the end, the increase in thermal energy must be less than the decrease in chemical potential energy. The decrease in chemical potential energy must equal the increase in thermal energy plus the increase in energy in the form of demagnetization. When the ferromagnet goes from magnetization to demagnetization there must be an equal decrease in thermal energy for energy to be conserved (... since there are no other energy change options in this system). [Does anyone have a site showing this is true or not?] Now, two magnetically aligned magnets are close to one another but some distance apart. There is a certain amount of potential energy between them. The packet of chemicals is closer to one of the magnets than the other. The chemicals are exposed to one another, and one of the two magnets is demagnetized. There was a certain amount of potential energy between them due to mutual attraction, and now there is no potential energy between them due to mutual attraction. (The magnets are far enough away from one another so that the magnetic field of the non-demagnetized magnet is not strong enough to keep the other magnet magnetized, but not so far so that there isn’t some (even if a very tiny) attraction between the two magnets before the demagnetization.) The magnets are in one another’s magnetic field. EN3 When the one magnet is demagnetized, it is immediately cut off from the magnetic field of the other. While for the other non-demagnetized magnet, it may take some time (at the speed of light or less, presumably) for it to then be cut off from the magnetic field of the already demagnetized magnet even though it has already been demagnetized. (And, at the most, or at the earliest, the other non-demagnetized magnet is cut off from the mutual attraction at the same instant the demagnetized magnet is.) All of the same energy changes occur as when there was with just one magnet, but with two magnets there is also one additional energy change. There is a decrease in chemical potential energy. There is an increase in thermal energy. There is an increase in energy in the form of demagnetization. And there is a change in the amount of potential energy due to mutual attraction between the two magnets. And so, for energy to be conserved, in the end, the decrease in chemical potential energy must equal the increase in thermal energy plus the increase in energy in the form of demagnetization ... plus or minus (or neither) the change in potential energy between the two magnets due to their loss of mutual attraction (depending on how the potential energy between them in this situation is defined). (If the potential energy between them due to mutual attraction is positive then there needs to be an additional decrease in thermal energy, if the potential energy between them due to mutual attraction is negative then there needs to be an additional increase in thermal energy, and if the amount of potential energy between them is 0 then there needs to be no change in the amount of thermal energy, to then offset the change (or no change) in the potential energy between them due to the loss of mutual attraction.) EN4 The same thing is done again, but this time, from the other side. The same dynamics will occur in the inverse. And, so, the same conservation of energy analysis applies. Now, it is done again for the third time, but this time the two magnets are simultaneously demagnetized. At the moment of each magnet’s demagnetization each magnet is immediately cut off from the magnetic field of the other. This lack of mutual attraction then makes its way back across the distance of the field, but the other magnet has also already been cut off from the magnetic field and so is already in the state of lack of mutual attraction. When one of the magnets is demagnetized it is instantly cut off from the shared magnetic field and so whether the other magnet is demagnetized at the same time or whether it remains magnetized is immaterial the demagnetized magnet (or magnets). When only one of the two magnets is demagnetized, for energy to be conserved, the decrease in chemical potential energy must equal the increase in thermal energy plus the increase in energy in the form of demagnetization ... plus or minus (or neither) the change in potential energy between them due to their mutual attraction. And since whether or not the other magnet remains magnetized or is simultaneously demagnetized is immaterial (due to the demagnetized magnet or magnets being cut off from the magnetic field at the instant of its own demagnetization), then the same energy changes physically must occur with each magnet regardless of the status of the other magnet (whether still magnetized or simultaneously demagnetized). So, whether or not the other magnet is simultaneously demagnetized, with each magnet and each packet of chemicals, there is initially an equal increase in thermal energy as there is a decrease in chemical potential energy. But upon the instance of demagnetization, with each magnet, there must be a decrease in this otherwise increased thermal energy to offset the increased energy in the form of demagnetization. And, with each magnet, simultaneously demagnetized or not, there must be an increase or a decrease (or neither) in another form of energy (such as thermal energy) to offset the change in potential energy due to the loss of mutual attraction between the magnets. (Again, whether the other magnet remains magnetized or is simultaneously demagnetized is immaterial.) When one magnet was demagnetized, the loss of mutual attraction, and the potential energy that goes with that, between the two magnets must be accounted for with energy changes with the one demagnetized magnet alone (... there are no other energy change options). But, since upon the instance of demagnetization whether the other magnet remains magnetized or not is immaterial, whatever physical process one demagnetized magnet goes through when the other is not must be the same physical process each magnet goes through when each magnet is demagnetized while the other is also simultaneously demagnetized (... since the magnetized or not magnetized state of the other magnet is immaterial upon the instance of demagnetization). But this means when the two magnets are simultaneously demagnetized the offsetting energy change for the change in the potential energy due to mutual attraction between them occurs twice (once for each magnet) while the actual change in the potential energy between them due to mutual attraction only occurs once in physical reality. And so, the logic required to find energy is conserved in the first scenario (there is a change in thermal energy with the one demagnetized magnet that offsets the full change in potential energy between the two magnets due to the loss of mutual attraction), then (sense the same physical process must occur in both cases given that the magnetization or not status of the other magnet is immaterial) including this same physical process in the second scenario (there is the same change in thermal energy with each magnet simultaneously demagnetized; while only one of these two changes alone would have offset the total amount of change in potential energy between them) means energy is not conserved in this second scenario. With one exception, maybe. If the amount of potential energy between the two magnets due to mutual attraction is set to 0 at the time of either of one of the two magnets’ demagnetization, then 0 amount of potential energy becomes no potential energy in both the one demagnetized and in the both simultaneously demagnetized cases. And so, in a sense, energy is conserved. (And it just takes a moment for this new reality to make its way to the non-demagnetized magnet in the one demagnetized case while not (but rather instantaneous for both) in the simultaneously demagnetized case.) But this, at the very least, seems like somewhat of a dodge. There is 0 amount of potential energy between them before demagnetization in the sense of in relation to other amounts of potential energy. It is not that 0 amount of potential energy is no potential energy. There was some amount (even if 0 amount) of potential energy before the demagnetization and then that existent energy (whatever amount) is gone. And, even if this somewhat of a dodge works, it only works if there is only one set of magnets. If there are two sets of magnets in the same closed system, and if the distance between the two in each set is different, then this somewhat of a dodge doesn’t work. Only one set can be designated as 0 amount of potential energy between them, which necessarily means the amount of potential energy between the two in the other set is either a positive or negative amount of energy. And so, with a non-zero amount of potential energy between at least the two magnets in of one of the sets, the change in this positive or negative energy between them cannot both lead to energy conserved in the two cases where, one, the other magnet (in this set) remains magnetized and where, two, the other magnet (in this set) is simultaneously demagnetized. The conservation of energy analysis issue is not yet resolved. ? --- (The only other thing I can think of is that in the case where only one magnet is demagnetized, the retreating field lines retreating towards the still magnetized magnet, somehow cause the still magnetized magnet to change energetically in a way that does not occur when they are both cut off from the field simultaneously and so do not encounter the retreating field lines of the other and thus don’t have the same energy change, but it’s hard for me to see a path back to conservation of energy via this route. ? ) --- EN1: A ferromagnet spontaneously magnetically aligns itself within itself when below a certain temperature, while becomes magnetically disaligned within itself when above this temperature, unless there is another strong magnetic field nearby to keep the heated ferromagnetic still magnetically aligned. EN2: It is understood that the magnetic dipoles within the ferromagnet will spontaneously magnetically align unless there is a change, such as in increase in thermal energy, which then places them into a state of misalignment; thus making the demagnetized state (as opposed to the magnetized state) the higher energy state. EN3: The U shaped magnetic field lines were meant to be simple symbol of the retreating field lines. A more accurate drawing would have used oval field lines. A more accurate drawing would have included the straight field lines from one pole on each magnet to the two opposite poles on each magnet. And a more accurate drawing would have also included the field lines from each of the two magnets that are out and away from one another on their other sides. EN4: One of these three energy options must occur while the other two do not and so, upon physical experimentation, this (the actual amount of potential energy present between the two magnets due to mutual attraction) is no longer a matter of stipulation. However, this discussion here occurs before physical experimentation. This is part of the “forming a hypothesis” stage where one’s logic must work out within itself when forming that hypothesis about the physical world.

There is a next step to the logic I was working out here. I started out thinking about something somewhat similar to the topic is this thread but now I've stepped too far away from it, and so I'll start a new thread, with the next step in the logic.

My guess would be that magnetic attraction at a distance is not instantaneous, and that the non-demagnetized magnet would continue to accelerate for an additional moment as the “information change” makes its way across the distance between them. However, if that is the case then there is a conservation of energy analysis issue. In the first example, when the two magnets reach a certain velocity they are both demagnetized and so they both stop accelerating and so they then both continue on at this certain velocity. While, in the second example, when the two magnets reach that same certain velocity one is demagnetized but not the other and so the one stops accelerating and continues on at the same certain velocity while the other one continues to accelerate for an additional moment and so then stops accelerating and then continues on at a greater velocity. This means in the second case there is more kinetic energy in the end than in the first case. And so, for energy to be conserved, there must be a decrease in another form of energy in the second case that does not occur in the first case. And the only possible candidate in this scenario to be that other form of energy is thermal energy. So, does it take more energy to demagnetize one ferromagnet before then demagnetizing the other and less energy to demagnetize them at the same time (which would mean in the second case there less thermal energy which then offsets the greater amount of kinetic energy)? Or, if energy is to be conserved, does this mean magnetic attraction at a distance must be instantaneous? ?

The second question in the original post in this thread can also apply to the demagnetized ferromagnets example. In the above example both ferromagnets are demagnetized, but what if you just demagnetized one? (Perhaps the temperature increase occurs closer to one of the ferromagnets first before then dissipating out to the other.) The demagnetized one, it seems, should instantly stop accelerating since it is instantly disconnected from the mutual attraction. But what about the other non-demagnetized one? Does it continue to accelerate for a moment longer as the “information” of no longer mutual magnetic attraction makes its way across the distance between them? Or is the mutual attraction instantaneous at a distance and so is instantaneous for both and so there is not an additional moment of acceleration with the non-demagnetized magnet? ? (The magnets would need to be far enough apart so that the magnetic field of the non-demagnetized one is not strong enough to keep the demagnetized magnet above it Curie temperature magnetically aligned, but not so far so that there isn't (wasn't) some (even if only slightly) mutual attraction between them accelerating them towards one another.)

Yes. I realize you were just speculating, but for the conservation of energy logic to work, then, one, in the end the increase in thermal energy must be less than the decrease in chemical potential energy (since the demagnetized state is a higher energy state than the magnetized state and so it takes energy to demagnetize the two ferromagnets), and, two, when the two ferromagnets are closer together it takes more energy to demagnetize them than when they are further apart (and so in the end in the one case there is an increase in thermal energy and no kinetic energy and in the end in the other case there is a lesser increase in thermal energy and some kinetic energy). (And the greater amount of thermal energy in the one case must equal the amount of kinetic energy in the other case plus the greater loss of potential energy between the two magnets.) Again, I realize this is just speculation, but it must be for the logic to work. Is there a link to somewhere showing this is not just speculation but is in fact the case? --- (Again, I apologize if I’ve diverted this thread from its original intent.)

This may be different from what you’re thinking about, but I think I may have thought through something similar. ---- Say you have two magnetically aligned magnets close to one another but some distance apart. There is a certain amount of potential energy between them. If they are allowed move they will set each other into motion due to mutual attraction. There will be an increase in kinetic energy and an equal decrease in potential energy. Now, say, there are two chemicals in a packet nearby and when these chemicals are exposed to one another thermal energy is generated (there is a decrease in chemical potential energy and an equal increase in thermal energy). And, say, the amount of thermal energy generated is greater than the Curie temperature of the two ferromagnets. (There are no other strong magnetic fields nearby in this closed system.) If the chemicals are exposed to one another before the magnets are allowed to set each other into motion then the amount of potential energy between them is gone. However, if the chemicals are exposed to one another after the magnets have set each other into motion the kinetic energy (that came from an equal decrease in potential energy) is not gone. So, in the end, after ferromagnets have been raised above their Curie temperatures, there must be more of another form of energy (such as thermal energy) in the first case and less of another form of energy (such as thermal energy) in the second case. Is there more thermal energy in the end in the first case and less thermal energy in the end in the second case? (One possible way to resolve this is to set the amount of potential energy between the two magnets at the start at 0. This way, in the first case, when the potential energy between them is then gone, 0 amount of potential energy becomes no potential energy. However, this does resolve the conservation of energy analysis in the second case because the positive amount of kinetic energy remains but the offsetting decrease in potential energy (negative potential energy) is then gone.) So, when two ferromagnets are some distance apart and then raised above their Curie temperatures is more heat generated when they are further apart or when two ferromagnets are some distance apart and then raised above their Curie temperatures is more heat absorbed when they are closer together? It seems to me one or the other must be the case for energy to be conserved. Is this the case? ---- (I’m sorry if this is totally different from what you are thinking about here in this thread, but it seemed similar.)

Yes, airfoils are complicated things. And I probably should stay away from them. I know most of you don’t think I’m listening and learning from this discussion. But I have. I still don’t know how to reconcile the conservation of energy analysis, but I am further along than when I started this discussion. I have another conservation of energy analysis question. And I believe I could learn from a discussion of that. It’s about a different part of our physical world, so I’ll not put it here but rather in a new thread. And any additional help on that would be greatly appreciated.

I read post 18 several times and worked on a couple of different replies. But I kept finding myself writing way too lengthy replies trying to return this conversation away from what I believe are tangential points (valid in their own right, but tangential to the one simple aspect of lift I am having an issue with when it comes to the conservation of energy analysis). And all my attempts just ended up sounding like I’m not taking the other people’s points here seriously and just reiterating something already shown to have been incorrect over and over again. So, I’m not sure how to reply. But, once before you asked me to shorten my original question/issue. And I said I couldn’t. But maybe I can in the form of some simple questions. 1. If the force from the fluid pressure pushing up on the bottom of a submerged object is greater than the weight of the object plus the force from the fluid pressure pushing down on the top of it, will it rise (if it is free to rise)? 2. When a less dense solid object (overall density) is submerged in a more dense fluid is the force from the fluid pressure pushing up on the bottom of it is greater than the weight of the object plus the force from the fluid pressure pushing down on the top of it (due to fluid statics)? 3. When a more dense solid object is submerged in a less dense fluid is the force from the fluid pressure pushing up on the bottom of it is less than the weight of the object plus the force from the fluid pressure pushing down on the top of it (due to fluid statics)? 4. If a less dense submerged object rises in a more dense surrounding fluid is the increase in kinetic energy of the rising object and falling fluid balanced out by an equal decrease in gravitational potential energy (ignoring losses to thermal energy)? 5. If, due to the different decreases in pressures on the top and bottom of a horizontally moving airfoil, the force from the fluid pressure pushing up on the bottom of it is more than the weight of the object plus the force from the fluid pressure pushing down on the top of it, will the more dense airfoil rise (due to this aspect of fluid dynamics (Bernoulli’s principle))? Did I make the issue/problem any clearer? I know it may be kind of rude to ask someone to answer a bunch of questions, but they are only yes/no questions, and I hope they help put a finer point on my problem. ---- In regards to post 18. Perhaps you and I disagree, but I believe that to understand all of lift then each part of lift must be understood individually and not in some gestalt way. And I’m not bothered by the other aspects of lift. With each of the other dynamics that contribute to lift I can reason my way to how energy is conserved. And if you’d like to talk about those aspects and how energy is conserved, we can. But when it comes to the buoyancy contribution to lift and the fluid dynamic changes in buoyancy with a horizontally moving submerged body in the shape of an airfoil, I’m stuck. ---- And we can talk about thrust but it is really beyond the scope of the issue. 1. If it is within the realm of possibilities for a body to have been set in motion while the source of that motion is unknown, then it is so stipulated here. 2. If it is within the realm of possibilities for an airfoil to have been set into motion beyond that necessary for lift while also being held down and then later allowed to rise, while another airfoil is in the same situation but never allowed to rise, then it is so stipulated here. There is no need to talk about thrust, I don’t think, but we can. --- The question as laid out comes to an end before the rising airfoil starts to fall. ---- And if you saying that the lift of an airfoil comes from the same lift in a rocket, in that it is the engines themselves pushing the body vertical and not horizontal, then we disagree.

I was wrong when I wrote: “If so, I disagree. The upward buoyant force on the airfoil is a force and not energy.” There is also energy involved in this situation. When a ball is submerged in a column of water, there is an upward buoyant force on it, and if let go it will rise. Energy is the ability to do work. For the ball to be moved (increase in kinetic energy) there must be a decrease in another form of energy. And there is. The more dense fluid displaced upwards by the less dense ball is an amount of gravitational potential energy. And as the ball rises and speeds up there is an equal decrease in gravitational potential energy in the form of the falling water (ignoring friction and losses to thermal energy and the movement of the fluid itself). And so for the airfoil to rise (in part) due to the different decreases in pressure pushing down on top of it and in pressure pushing up on the bottom of it creating a greater upward buoyant force on the airfoil (which, if the airfoil is light enough could lift the airfoil on its own regardless of the other factors contributing to lift) must come from a decrease in another form of energy to offset the increase in kinetic energy, as with the rising submerged ball. But, with the rising submerged ball that came from a decrease in the form of the more dense fluid falling and thus a decrease in gravitational potential energy, but here the airfoil is more dense than the surrounding fluid and so as kinetic energy increases in the form of the now also vertically moving airfoil there is not a corresponding decrease in gravitational potential energy, but rather the opposite. I have a better understanding of this analysis now thanks to this conversation, but I’m still missing something. ?

I understand that a complete analysis of lift requires looking at every factor that contributes to lift. And I understand much of how energy is conserved when it comes to most aspects of lift (such as when there is an angle of attack and there is a redirection of airflow downwards as it collides with the airfoil and moves it upwards). But, regardless of all the other factors involved, there is a greater decrease in pressure pushing down on the top of the airfoil than there is a decrease in pressure pushing up on the bottom of the airfoil and so there is a greater upward “buoyant force” on the airfoil and this is one of the factors contributing to lift. And if this force leads to an increase in gravitational potential energy (the rising airfoil) then there needs to be a decrease in another form of energy that does not also decrease when there is no increase in gravitational potential energy (the non-rising airfoil). What is it? ---- If it is within the realm of possibilities for something to be within an isolated system, then it is so stipulated that the airfoils are in an isolated system. 1 In both the rising and non-rising cases the airfoils, their shape and weight, are exactly the same. It’s just that in the non-rising case there is something (a frictionless track) holding it down. 2 In both the rising and non-rising cases the airfoils start out in motion and in the exact same positions and with the same velocities. There is no additional thrust keeping them going. 3 In a real friction-filled world there will be a loss of kinetic energy to thermal energy. But for energy to be conserved in the rising case versus the non-rising case via thermal energy, this means in the rising case there must be a decrease in thermal energy that does not occur in the non-rising case or this means less of an increase in thermal energy in the rising case than in the non-rising case and these dynamics are not imaginable. 4 Having a greater “buoyant force” means greater lift, and this force is allowed to lead to an increase in gravitational potential energy in the one case and not in the other. Where is the offsetting decrease in another form of energy in the rising case?