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Homework Help: Effect of water upthurst in vacuum conditions

  1. Nov 3, 2011 #1
    1. The problem statement, all variables and given/known data

    A sphere is enclosed in a bell jar half filled with water. The sphere floats. Air is pumped out to create a vacuum above the water inside the bell jar. Will the sphere float in the same way, float better or will it sink?

    2. Relevant equations


    3. The attempt at a solution

    My guess is that since there are no air particles pushing down on the water surface the sphere should sink more maybe not completely. Is this correct?
  2. jcsd
  3. Nov 3, 2011 #2


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    Staff: Mentor

    There are also no air particles pushing down on the portion of the sphere that's above the water line. So has there been any net change to the equilibrium?
  4. Nov 3, 2011 #3
    I had omitted that fact! So the sphere would float just with or without vacuum above the water since both the pressure on the water and on the sphere are being reduced. Thank you so much.
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