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Homework Help: Need Hmwk Help . Fluid mechanics, Fluids in Motion, Pressure

  1. Dec 11, 2009 #1
    College Physics

    1. The problem statement, all variables and given/known data

    The figure shows a syringe with a 4.0-cm-long needle, filled with water at 20celsius.
    What is the gauge pressure of the water at the point P, where the needle meets the wider chamber of the syringe?

    http://session.masteringphysics.com/problemAsset/1014207/7/jfk.Figure.P13.38.jpg


    2. Relevant equations

    Bernoulli's Equation


    3. The attempt at a solution
    I haven't even reached a solution yet because I am totally lost....
    I just need some guidance/help working through the problem.
     
  2. jcsd
  3. Dec 11, 2009 #2
    The answer is 3200 Pa.

    However, I do not know how to arrive at that solution. I'd reallllyyyyy appreciate it if someone could walk me through it, step by step.
     
  4. Dec 11, 2009 #3

    ideasrule

    User Avatar
    Homework Helper

    Use Bernoulli's principle. Apply it to the two points where you have the most information: just outside the narrow tube, and very near the piston. You can figure out the speed of the piston from the volume continuity equation.
     
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