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A question of lifting bodies underwater

  1. Apr 11, 2007 #1
    If I have two rubber coated kevlar balls, one is filled with air and the other has a gas like helium in it, if submerged underwater, would the ball with helium be harder to keep underwater than the air filled ball would be, or would they be equal in their buoyancy?
    Also is helium easier to compress than air, I would imagine it would be but I don't have any schooling in this field.
    Thanks for the site, and any answers to my questions.
  2. jcsd
  3. Apr 11, 2007 #2


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    Staff: Mentor

    The way the definition of buoyancy works, the buoyancy is the same - what is different is the weight of the two gas-filled spheres. Since the one filled with helium is lighter, the net force required to keep it submerged is higher.
  4. Apr 12, 2007 #3
    Russ_watters is right. But you cannot feel the difference. You must measure the two lifting forces with a very precise device. The difference in lift is about 0.1%.
  5. Apr 12, 2007 #4
    Thanks for the info!
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