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Homework Help: Buoyance of oil and water

  1. Apr 18, 2007 #1
    I have 2 liquids, Oil and water together in the beaker.

    Assuming both liquids are non mixable

    I push a block into the water and it floats at halfway between the Oil and the water

    See the attachment and please help me I'm stuck and
    passing the class depend on this particular problem ...

    Attached Files:

  2. jcsd
  3. Apr 18, 2007 #2


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    Gold Member

    Do you about Archimedes principle ? A body floats at the level where the weight of the submerged part equals the weight of the displaced liquid.

    I think you got your specific gravities the wrong way round.
  4. Apr 18, 2007 #3
    Yes I'm talking about Archimedes principle..

    The Professor gave us this question as it is.. ireally tried to resolve it without
    any success. any suggestions??
  5. Apr 18, 2007 #4
    Mentz pointed out one problem. Another, even if reversed, Water has an sg=1.0, not .3 or .8

    Finally as posed and assuming that the block is homogeneous and density greater than either fluid, the object would sink. I'd put this one away until you get clarification.
  6. Apr 18, 2007 #5
    I'm sorry it is not water the question was two liquids.
    Any liquids. assuming they are 0.3 0.8 i used water and
    oil just to clear out which one is on the top and which
    one is on the bottom.
    So ignore the names.
    The question didn't say anything about the object's density
    the question only wants to know the % of the part that is
    in the oil..
  7. Apr 18, 2007 #6


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    My reading of the question is that the block has sg = 0.93. So it would sink in the more dense liquid if it wasn't partly supported by the upper liquid.

    Assume the block sinks to a depth x, and has top area A. You get an equation in x because A will cancel out.
  8. Apr 18, 2007 #7
    maybe this is a deep problem after all, but the diagram shows a density greater than either fluid, but adds to it "in water part". If the density is greater than either fluid it will sink as in completely. Now if the density were somewhere between the two, ok, it should sit in between. But whats most confusing is you state that the object is 1/2 in 1/2 out, but the diagram asks for what percentage is in the oil? I personally (and this is without any mean spirited intention), is that you probably should repeat the course. Our bailing you out at the last minute is not apt to be of value to anyone.
  9. Apr 19, 2007 #8
    Can Any One Help me with this Question????
  10. Apr 19, 2007 #9
    by the looks of that picture ( 50%) heh
  11. Apr 22, 2007 #10
    Help anyone
  12. Apr 22, 2007 #11
    help help
  13. Apr 22, 2007 #12
    sorry, I wish I could help, but never took fluids yet. I agree with zenparticle though:shy:
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