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Homework Help: Viscosity,Fluid flow and terimal velocity

  1. Dec 1, 2011 #1
    1. The problem statement, all variables and given/known data
    When does Fb(Buoyancy force) equal the drag force(FD)?
    and Fb+FD=Fg

    2. Relevant equations
    Fb=density of water times volume of water times 9.80 m/s^2
    FD=6pi times viscosity times radius times v
    Fg=mg
    3. The attempt at a solution
    All ik is the solid has 2 be in the air going to the water but idk how 2 really prove that please help me
     
  2. jcsd
  3. Dec 2, 2011 #2
    This problem is really confusing. Do we have a ball falling in water? Not sure what is going on here.
     
  4. Dec 2, 2011 #3

    ehild

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    Homework Helper

    It is a sphere of radius r moving with speed v in a fluid of viscosity η. The drag force is FD=6πηrv.
    The buoyant force is FB=ρVg, where ρ is the density of the liquid and V is the volume of the sphere.

    ehild

    PS: ChunkymonkeyI, what did you mean: "All ik is the solid has 2 be in the air going to the water but idk how 2 really prove that please help me" We use English here.
     
    Last edited: Dec 2, 2011
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