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I Measuring boyancy

  1. Jul 18, 2016 #1
    When I take a beachball and force it underwater it is almost impossible due to the upward force of the buoyancy. Is there a way to determine what that upward force is based on volume of the object, or viscosity of the liquid (including air and balloons).

    How does one figure that? Since the weight of the object being "floated" is equal to the volume of the water displaced wouldn't the force to push the beach ball underwater equal to the weight of the water displaced by the ball in units of force instead of weight?

  2. jcsd
  3. Jul 18, 2016 #2


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    Your question is confusing. Are you looking for a way to calculate the buoyant force, or are you trying to find a way to measure the buoyant force?

    If the former, then I'll first ask you if you are familiar with Archimedes principle. If it is the latter, attach a spring to the balloon the measure the pull on the spring when they are all under water.

  4. Jul 18, 2016 #3


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    Yes (minus the weight of the ball, negligible for a beach ball).
  5. Jul 18, 2016 #4


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    The calculation of the weight of the displaced water should be about right. If you want accuracy, weigh the beachball and subtract it. Remember that the beachball is compressible, so it will displace less water than if you measure it's size in the air. (I don't know how big the difference is.)
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