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Fluid Mechanics problem

  1. May 12, 2007 #1
    1. The problem statement, all variables and given/known data

    How big must the external force be so that the speed u remains constant at 5m/s?

    2. Relevant equations

    Newton's second:

    \frac{\partial}{\partial t}\int_{CV} \overrightarrow{V}\rho dV+\int_{CS} \overrightarrow{V}\rho \overrightarrow{V} \overrightarrow{dA}[/tex]

    3. The attempt at a solution

    (1) Steady Flow
    (2) Incompressible Flow
    (3) Uniform flow at each section where fluid crosses the CV boundaries
    (4) No body force (?)

    I shorten it to :

    \int_{CS} u \rho \overrightarrow{V} \overrightarrow{dA}[/tex]

    [tex]F_R=u|\rho V A| + F_N \mu_k[/tex]

    After inserting the given values I get


    - I'm not sure at all if I'm thinking correctly. I would really appreciate if someone could check my answer. Thanks!
  2. jcsd
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