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I Does Increased Pressure Affect Buoyancy?

  1. Jul 27, 2018 #1
    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?
     
  2. jcsd
  3. Jul 27, 2018 #2

    anorlunda

    Staff: Mentor

    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.
     
  4. Jul 27, 2018 #3

    Charles Link

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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.
     
  5. Jul 27, 2018 #4

    Janus

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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?
     
  6. Jul 27, 2018 #5
    Thanks, everyone.
     
  7. Jul 27, 2018 #6
    Please see @Charles Link's answer (which is correct).
     
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