Baluncore
Science Advisor
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Fail while repeating the experiment, by balancing two identical folded garbage bags.
Almost fill one bag with air by holding open the neck while moving it through the air, (so it does not gain extra moisture from lungs, and you do not hyperventilate).
Tie off the opening, without compressing the contents.
Since buoyancy in atmosphere is 1:1 with the contained air, the weights will still balance.
This contradicts the balloon experiment.
We know that it is the compressed air in the balloon that is more dense than the atmosphere.
So now the fun begins. Balance two elastic balloons, Inflate one just slightly, the other to maybe twice the diameter. Which will weigh more on the balance?
To answer that question you must realize that the pressure (and so the density) of the gas in a balloon is reduced as it is inflated. Notice how hard it is to start inflating an elastic balloon, but it gets easier as the radius of curvature increases and the pressure falls. Is there some ratio where the large and small balloons balance?
Almost fill one bag with air by holding open the neck while moving it through the air, (so it does not gain extra moisture from lungs, and you do not hyperventilate).
Tie off the opening, without compressing the contents.
Since buoyancy in atmosphere is 1:1 with the contained air, the weights will still balance.
This contradicts the balloon experiment.
We know that it is the compressed air in the balloon that is more dense than the atmosphere.
So now the fun begins. Balance two elastic balloons, Inflate one just slightly, the other to maybe twice the diameter. Which will weigh more on the balance?
To answer that question you must realize that the pressure (and so the density) of the gas in a balloon is reduced as it is inflated. Notice how hard it is to start inflating an elastic balloon, but it gets easier as the radius of curvature increases and the pressure falls. Is there some ratio where the large and small balloons balance?