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Homework Help: Fluid Mechanics of water and oil

  1. Mar 31, 2005 #1
    Here's the question: Water and then oil are poured into a U-shaped tube, open at both ends, and do not mix. They come to equilibrium as shown in the figure below, where y oil = 26.9 cm and y water=18.6 cm. What is the density of the oil? (Take the density of water as 1000 kg/m3.)

    I know that I need to use the P= Po+pgh somewhere and that where the two liquids are at equal height the pressure below that is equal... but I can't seem to get the right answer. I know it is simple- so can anyone help?
  2. jcsd
  3. Apr 1, 2005 #2


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    The two fluids are in equilibrium. Therefore their weights must be equal and opposite. Do a simple FBD and solve for the weight of oil required to counter the weight of the water.

    BTW...there was no diagram. Do you know the correct answer?
    Last edited: Apr 1, 2005
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