KingKong Posted October 23, 2004 Share Posted October 23, 2004 How does gravity follow the law of energy conservation? Just wondering... don`t hit me Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 23, 2004 Share Posted October 23, 2004 well technically I don't think Newtonian gravitation does however in "einsteinian?" gravity both objects exert a gravitational pull on each other equivalent to there mass by the way the mass(energy) warps spacetime if you are asking if that means it doesn't follow conservation of energy I believe it doesn't really have to its kind of like marbles rolling down a hill the way einsteinian gravity works I know in current laws of electromagnetism two particles with a charge will exchange a photon with eachother which will cause them to either become closer or go further away. according to physisists this doesn't violate conservation of energy because they both lose and gain a photon thus they don't lose energy 1 recieved minus 1 sent= 0 each reaction is equal independant of distance its just that the probbility of the two particles exchanging a photon becomes less by the square of the distance (i believe correct me if I'm wrong) so a system of particles like two blocks positivly charged will exert a repulsive force on each other that grows less by the square of the distance because fewer particles are exchanging photons at that distance. each reaction is equal a proton and electron exert an equal force of attraction on each other despite the difference in size. so the photon's exchanged are equal in energy to the force of attraction (or something like that) I belive quantum gravity is an attempt to find a particle (graviton) that does the same thing that the photon does in electromagnetism Link to comment Share on other sites More sharing options...
Cap'n Refsmmat Posted October 23, 2004 Share Posted October 23, 2004 Actually it does. Where does the energy that makes it fall come from? The energy that got it up that high in the first place. If you would jump off of a cliff, that energy came from you climbing up it. Link to comment Share on other sites More sharing options...
KingKong Posted October 24, 2004 Author Share Posted October 24, 2004 "If you would jump off of a cliff, that energy came from you climbing up it." So you are saying that if i climb a latter it somhow "charges" gravity? Like a bungie rope? By the way, thanks Luke. Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 you are reffering to potential energy which does not exist a chemical reaction moved energy in electrons around to create heat and to move things around in your muscle cells then your cells in your muscles worked in coordination and moved you up the hill to the cliff edge. as you stand over the cliff gravity is pulling down on you the entire time. however the gravitational force is ballanced by the electromagnetic force which is some 200x stronger, at that close of a distance when you jump off, there is no longer the electromagnetic holding you up you fall at a fixed rate of 9.9? ft/sec (gravity does change over time but it takes longer for the force to lesson (as in miles instead of inches) your welcome kingkong Link to comment Share on other sites More sharing options...
Sayonara Posted October 24, 2004 Share Posted October 24, 2004 you are reffering to potential energy which does not exist Quoi? Link to comment Share on other sites More sharing options...
Ophiolite Posted October 24, 2004 Share Posted October 24, 2004 you are reffering to potential energy which does not exist Quoi?Double Quoi? with a big feathery hat on! I guess if it doesn't exist, neither does kinetic energy, so we can all go out and drive as fast as we want with impunity. Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 kinetic energy does exist there is no reason why kinetic energy shouldn't exist it requires a certain amount of energy to accelerate an object to a certain speed why should potential energy exist? give me one situation where potential energy should exist I am unfamiliar with any math that may be involved with potential energy although the concept of potential energy could be trying to get at the idea that all work energy requires energy ie it comes from somewhere. such as it takes a certain amount of energy to accelerate an object to a higher velocity. although, potential energy as in a ball on top of a latter has more potential energy than a ball on the floor does not exist if you can prove me wrong about potential energy then I will be quiet and accept ignorance Link to comment Share on other sites More sharing options...
Sayonara Posted October 24, 2004 Share Posted October 24, 2004 What about all the various scenarios in physics where potential energy is required to balance equations? You need to fix all the equations you just broke by declaring potential energy non-existent. Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 find one equation that needs to be balanced by the adding of potential energy because if you say the potential energy of you walking up the hill gives you the energy to fall down then that is a falsehood, I will give you two reasons why if you have potential energy from coming up the hill then you standing on top of the hill you should still be gaining potential energy. because you are still being accelerated by gravity downwards and anouther force is acting to keep you vertical. thus when you fall you should use far more force then it took you to go up the hill because you are still experiencing the force of gravity and you are still being propeled upward in a new hypothetical situation if the marble magicly came into existance on the top of the middle of thin air. if the energy to fall is taken from the energy to rise then the marble shouldn't fall. but I am willing to bet you $100 that it will in fact fall If you really want a real world situation like the above one. Take a photon streaking through interstellar space then it comes under the effect of the gravitional field of a black hole. The photon will be drawn closer to the black hole. did the photon exert energy fighting the field before falling in? no, it didn't therefore ounce more if potential energy is real then the photon should not be effected by the gravitational force of a black hole. Link to comment Share on other sites More sharing options...
Sayonara Posted October 24, 2004 Share Posted October 24, 2004 find one equation that needs to be balanced by the adding of potential energy. Any that deals with the motion of objects relative to the position of other objects, afaik. According to you, hydroelectric dams don't work and the pendulum is mere fantasy. Unless of course you are right, and conservation of energy is broken, which would be a bit of a shocker. Think of potential energy as the ability to do work, rather than as work being done. but I am willing to bet you $100 that it will in fact fall Well of course it will. Potential energy is not antigravity. Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 think of a hydrostatic dam or a pendulem as our hypothetical scenario. the water is elevated its being acelerated at 9.9ft/s so it will fall down so if you place a hole in a dam (hydrostatic damn) the water will fall through the hole and through a turbine generating electricity. the lack of potential energy has nothing to due with it falling or not as you said yourself "well of course it will. potential energy is not antigravity" therefore is there any need to have potential energy Link to comment Share on other sites More sharing options...
swansont Posted October 24, 2004 Share Posted October 24, 2004 the water is elevated its being acelerated at 9.9ft/s g=32 ft/s2 Nobody uses English units Three errors in one sentence. That's pretty efficient. Link to comment Share on other sites More sharing options...
swansont Posted October 24, 2004 Share Posted October 24, 2004 How does gravity follow the law of energy conservation? Why do you think it doesn't? Link to comment Share on other sites More sharing options...
swansont Posted October 24, 2004 Share Posted October 24, 2004 I am unfamiliar with any math that may be involved with potential energy although the concept of potential energy could be trying to get at the idea that all work energy requires energy ie it comes from somewhere. Yes' date=' the concept is derived from work and energy. That you are unfamilar with the math does not make potential energy nonexistant. But here's the math: dW= F (dot) dx Integrate the equation. If F is constant, W = F(dot)s cos(theta) for gravity, F = mg If you do work on a system in the presence of a field force, the energy has to go [i']somewhere[/i] Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 I was wrong about the gravitational constant as noted in my original post "9.9?/fps" I wasn't entirely sure about it in the case of a dam your saying that the energy that gravity is exerting on the water must go somewhere. however taht seems to be ignoring the fact that its being balanced by the electromagnetic force that the dam exerts on the water it seems perfectly logical to me that this is just a nice balance of force. the water molecules can only come so close to the dam before they are repulsed by the electromagnetic force that the atoms contained in the dam exert on the water. why do we need potential energy? Link to comment Share on other sites More sharing options...
Sayonara Posted October 24, 2004 Share Posted October 24, 2004 Do you not think it's the case that those electromagnetic forces would have the same effect if the water and the dam were not being subjected to gravity? Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 if the dam wasn't being subjected to gravity the electromagnetic forces in the water would try and force it to become as seperated as possible. everything on the earth would try and force itself apart. except for molecules and certain compounds that bind themselves together through the electromagnetic force gravity acts to force the water down towards the ground causing pressure (cummulative because each water molecule has weight and forces itself down against the electromagnetic force of the molecules below it). In this way the water at the bottom of the lake behind the dam is under much higher pressure than the water at the surface. However the electromagnetic force prevents the water from compressing down to a singularity. out of curiosity on the math you showed me is that for calculating the potential energy of a system or for calculating the gravity of a system Link to comment Share on other sites More sharing options...
Sayonara Posted October 24, 2004 Share Posted October 24, 2004 I don't think I did show you any maths. Are you referring to Swansont? Link to comment Share on other sites More sharing options...
KingKong Posted October 24, 2004 Author Share Posted October 24, 2004 Why do you think it doesn't? Well, gravity apears to go on forever. So I was wondering where it would come from. I did not say that I don`t think it does. Just asking for an explanation. Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 sorry, I guess I was reffering to swansont on that one Link to comment Share on other sites More sharing options...
swansont Posted October 24, 2004 Share Posted October 24, 2004 in the case of a dam your saying that the energy that gravity is exerting on the water must go somewhere. however taht seems to be ignoring the fact that its being balanced by the electromagnetic force that the dam exerts on the water it seems perfectly logical to me that this is just a nice balance of force. the water molecules can only come so close to the dam before they are repulsed by the electromagnetic force that the atoms contained in the dam exert on the water. why do we need potential energy? But in raising the water to some height, you have to do work. And when the water falls, it can do work. That's why we need potential energy. Link to comment Share on other sites More sharing options...
CPL.Luke Posted October 24, 2004 Share Posted October 24, 2004 I think I see what your saying now however, the energy does not flow into the water. as it is raised. because, this would imply that if the water just appeared magiclly in its elevated state it could not fall because it was never "charged" with work energy in order to fall. I understand that with conservation of energy energy can't dissapear, but it always goes somewhere. It is converted from chemical to kinetic (heat in this case) which then flows into the surrounding enviroment can you explain some of the equations that you posted, I'm curious if those are for calculating the potential energy or for calculating the strength of the field Link to comment Share on other sites More sharing options...
KingKong Posted October 25, 2004 Author Share Posted October 25, 2004 Let me get this straight. Originally posted by CPL.Luke well technically I don't think Newtonian gravitation does however in "einsteinian?" gravity both objects exert a gravitational pull on each other equivalent to there mass by the way the mass(energy) warps spacetime if you are asking if that means it doesn't follow conservation of energy I believe it doesn't really have to its kind of like marbles rolling down a hill the way einsteinian gravity works I know in current laws of electromagnetism two particles with a charge will exchange a photon with eachother which will cause them to either become closer or go further away. according to physisists this doesn't violate conservation of energy because they both lose and gain a photon thus they don't lose energy 1 recieved minus 1 sent= 0 each reaction is equal independant of distance its just that the probbility of the two particles exchanging a photon becomes less by the square of the distance (i believe correct me if I'm wrong) so a system of particles like two blocks positivly charged will exert a repulsive force on each other that grows less by the square of the distance because fewer particles are exchanging photons at that distance. each reaction is equal a proton and electron exert an equal force of attraction on each other despite the difference in size. so the photon's exchanged are equal in energy to the force of attraction (or something like that) I belive quantum gravity is an attempt to find a particle (graviton) that does the same thing that the photon does in electromagnetism Does everyone agrees with this? If not. Why? Link to comment Share on other sites More sharing options...
swansont Posted October 25, 2004 Share Posted October 25, 2004 No, I never said the energy "flowed into the water." The energy is is the water/earth system. Discussing the scenario where the water "just appears" is nonsensical; you are already violating energy conservation. You can't use it as a counter-argument to energy conservation! How does the energy appear as heat? Are you implying that if I carry a glass of water in an elevator that its temperature will increase? Link to comment Share on other sites More sharing options...
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