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Homework Help: Capillary Tube Problem

  1. May 12, 2014 #1
    1. The problem statement, all variables and given/known data

    A drip-irrigation emitter constructed of a coiled capillary tube is inserted into the wall of a drip irrigation line with a constant water pressure of 5 psi. Compute the required length of the emitter’s capillary tube to produce an emitter dripping rate of 2 litres per hour if the capillary tube diameter is 1mm.

    2. Relevant equations

    Pressure = Force * Area
    Volume of Cylinder = ∏ * Length *Radius^2

    3. The attempt at a solution

    I converted all the units into SI. I know I need to solve for length of the cylinder, but when I try to equal the cylinder dimensions to 5psi nothing works out. Just don't know how to approach the problem yet. Any help would be appreciated. Thanks.

    5 pounds/inch^2 = 34,473.7865 kg/ms^2
    2Litres/hour = 5.55x10^-7 m^3/s
    diameter = 1mm = 0.001m
    radius = 0.001m/2 = 0.0005m
  2. jcsd
  3. May 12, 2014 #2
    Hi Maxnormal. Welcome to Physics Forums!!!!

    Are you learning fluid mechanics? Have you learned about the Hagen -Poiseuille viscous flow equation?

  4. May 12, 2014 #3
    Hey! Right now I am learning Soil Physics. And I have not learned of that equation yet. Will I need that equation to solve the problem?
  5. May 12, 2014 #4
    Google it and see if it satisfies your needs.

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