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Homework Help: Bouyant force on a cube floating at the surface between water and oil?

  1. Nov 11, 2009 #1
    1. The problem statement, all variables and given/known data
    A cube of 15 cm is floating at the surface between water and oil. The oil has a density of 810 kg/m3. If the cube floats so that it is 52% in water and 48% in the oil, what is the mass of the cube and what is the buoyant force on the cube?

    2. Relevant equations
    Archimede's Principle
    Fb= densityfluidvfluidg

    3. The attempt at a solution
    Not sure how to find the mass of the cube when only the height of one side is given?
  2. jcsd
  3. Nov 11, 2009 #2


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    Science Advisor
    Homework Helper

    The cube is displacing it's own weight in oil and water.
    it might be simpler to think of it as two (almost ie 0.52/0.48) half cubes immersed in oil and water.
  4. Dec 1, 2009 #3
    fb = (1000*0.52+810*0.48)*0.15^3*9.8
    =30 N

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