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B Upthrust and Floating

  1. Nov 13, 2016 #1
    OKay I just want to confirm...It is written everywhere that if , in a liquid, the upthrust acting on an object is equal to its weight, it will float...If we consider an object taken deep into a liquid, and somehow its weight becomes equal to the upthrust acting on it, then it would just stay at that position..right??? Like it would keep its position and not rise to the surface of the liquid...
  2. jcsd
  3. Nov 13, 2016 #2


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    Yes, that's the idea. Then there is no net force pushing upwards. Newton's law.
  4. Nov 13, 2016 #3
    Thank you for your help....
  5. Nov 13, 2016 #4


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    Correct. The term used is "neutrally buoyant".

    It can sometimes be quite hard to achieve because if the object is displaced downwards slightly the increased pressure can compress the object making it more dense so it descends further. Likewise if it is displaced upwards the reduced pressure may cause it to expands making it less dense so it rises further. Temperature changes and also cause problems.

    Divers sometimes find it difficult to achieve and their lives sometimes depend on it...

  6. Nov 13, 2016 #5
    This is the purpose of a fish's swim bladder. They essentially fill a balloon to stay neutrally buoyant.
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