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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?


    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


    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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