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Buoyancy and Energy Conservation

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T3sl4co1l:
Right.  The buoyant force isn't constant, because air density isn't constant; you'd have to integrate over the altitude to see what work has been performed.

Tim

Zero999:

--- Quote from: Circlotron on May 20, 2020, 07:20:19 am ---
--- Quote from: Zero999 on May 19, 2020, 08:42:18 pm ---The balloon can only lift an object equal to the mass of the air inside it.

--- End quote ---
I would think it could lift a weight equal to the weight of the air the balloon displaces minus the weight of the gas or vacuum inside the balloon. Example - the balloon will lift a whole lot more if you place it underwater.

--- End quote ---
Yes, I should have said displacement.

Underwater is a good example. Imagine the balloon is deflated and underwater. The deeper it is, the more pressure and thus work will be required to displace the same volume of water, so lift the same mass.

msuffidy:
Wow thanks for all the good analysis. One other way of altering buoyancy may be mechanically compressing the balloon to make it less buoyant.

james_s:
You're falling into the same trap as all these other free energy/over unity guys. Adding additional complexity until you reach a point where you don't understand or can't keep track of all the factors and then pondering whether the system would actually work. It won't, the laws of physics will always win, even if you manage to obfuscate it from yourself, there will always be some factor that will stop it from working the way you imagine it might.

NiHaoMike:
I think that if the practicality problems were somehow overcome, the limiting factor is the finite (even if very large) amount of hydrogen available to run the process with. Hence it would not be perpetual motion any more than tidal power is perpetual motion.

--- Quote from: Zero999 on May 20, 2020, 12:19:20 pm ---Underwater is a good example. Imagine the balloon is deflated and underwater. The deeper it is, the more pressure and thus work will be required to displace the same volume of water, so lift the same mass.

--- End quote ---
Underwater, a volume of gas can lift far more weight than it can in air, thus increasing the energy that can be extracted from lift. So electrolyze water deep in the ocean to lift bags that power a generator. Or actually, forget the bags and just have a pipe to the surface, using the pressure of the water to pressurize the gas. Something doesn't seem right since you could burn the hydrogen after using the pressure, getting back water to allow the process to not use up anything.

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