Does Increased Pressure Affect Buoyancy?

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Discussion Overview

The discussion centers around the effects of increased pressure on the buoyancy of two metal spheres filled with helium at different pressures, specifically examining whether one sphere experiences a greater buoyant force than the other when submerged in air.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant proposes that to determine the buoyancy force, one must calculate the difference in weight between the air and the helium for the same volume and pressure.
  • Another participant asserts that the buoyant force is the same for both spheres, noting that the second sphere, filled with more helium, will weigh more, but the buoyant force is determined by the weight of the air displaced, as per Archimedes' principle.
  • A participant emphasizes that buoyancy results from the density difference between the object and the surrounding medium, questioning how compressing helium to higher pressure affects its density.
  • Another participant reiterates the point about buoyancy being related to density differences and asks about the implications of compressing helium at higher pressures.

Areas of Agreement / Disagreement

Participants express differing views on whether the buoyant force changes with increased helium pressure, indicating a lack of consensus on the matter.

Contextual Notes

The discussion does not resolve how the density of helium changes with pressure, nor does it clarify the implications for buoyancy in this specific scenario.

chemisthypnos
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Imagine that there are two metal spheres both with the same volumes and I am trying to get them to float up into the air. I fill the first sphere with 5 ATM of helium and I fill the second sphere with 6 ATM of helium. Will either sphere have a higher buoyancy force acting on it than the other sphere if we assume that the medium that the spheres are in is air?
 
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The way to calculate that is to find the difference in the weight of air to weight of helium for the same volume and same pressure..

You can look up the numbers and do the calculations yourself. Let us know your answer.
 
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The buoyant force is the same for both. The second sphere will weigh more because it has more helium inside of it. The air supplies the buoyant force, which is equal to the weight of the air displaced by the sphere by Archimedes principle. The helium inside the metal sphere does not supply the buoyant force. A balloon filled with helium floats because the helium is lighter than the air that gets displaced.
 
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Buoyancy is caused by a difference between the density of the buoyant object and the medium surrounding it. What happens to the density of helium if you compress it to a higher pressure?
 
Thanks, everyone.
 
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Janus said:
Buoyancy is caused by a difference between the density of the buoyant object and the medium surrounding it. What happens to the density of helium if you compress it to a higher pressure?
Please see @Charles Link's answer (which is correct).
 
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