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Help understanding the Viscosity Formula

  1. Sep 17, 2011 #1

    Hi there,
    We have some questions regarding the force it would take to keep a shaft moving in a tube at a constant velocity.

    I gather the formula we should use is:


    My understanding is that in this formula
    [tex]F[/tex] is the force required
    [tex]A[/tex] is the parallel surface area
    [tex]u[/tex] is the viscosity of the fluid
    [tex]dux/dy[/tex] is the slope of the velocity gradient.
    Since in the question the shaft is up to speed [tex]dux/dy=1[/tex]
    I punch in the numbers and the result I'm getting have been nonsensical so any clarification would be fantastic!!
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
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