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Homework Help: Fluids and viscous flow

  1. Nov 5, 2007 #1
    1. The problem statement, all variables and given/known data
    Water (n = 1.00 10-3 Pa·s) is flowing through a horizontal pipe with a volume flow rate of 0.029 m3/s. As the drawing shows, there are two vertical tubes that project from the pipe. From the data in the drawing, find the radius of the horizontal pipe.


    2. Relevant equations

    Q = πR^4(P1-P2) / 8nL

    3. The attempt at a solution

    0.029 = πR^4(0.045) / (8*10^-3 * .7)

    solve for R, multiply by 100. However, i dont get the right answer...

    What am i doing wrong? this seems like such a straightforward problem

    Attached Files:

  2. jcsd
  3. Nov 5, 2007 #2


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    Staff Emeritus
    Science Advisor

    Is the differential pressure, (P1 - P2), in the formula given as the head (height or depth) of water (0.045 m), or is it pressure, in which case [itex]\Delta[/itex]P = [itex]\rho[/itex]g[itex]\Delta[/itex]h, where [itex]\Delta[/itex]h is the difference in heights of the water columns, i.e. 0.045 m.
  4. Nov 5, 2007 #3
    oh maybe it's pgh. let me give it a second go.
  5. Nov 5, 2007 #4
    yes i got it right. thank you Astronuc for the fast reply! I owe you :)
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