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Homework Help: Fluids - find viscosity

  1. Nov 22, 2003 #1
    A tank of large area is filled with water to a depth of 0.6m. A hole of 6m^2 cross section in the bottom allows water to drain out in a continous stream. What is the rate at which water flows out the tank in m^3/s?
    This is how I figure the problem should be solved:
    Q= pi*r^4(p1-p2)/8L*viscosity

    Area= 6e-4m^2
    h= 0.6m
    P= rho*g*h= 1.00e3kg/m^3*9.8m/s^2*0.6m= 5880N/m^2
    what I can't figure out is how do I get viscosity from the area
  2. jcsd
  3. Nov 22, 2003 #2


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    Science Advisor

    Didn't you post this under a different forum?

    You CAN'T get "viscosity" from area. Viscosity is a phyical property of the fluid itself. If you really needed it you should look up the viscosity is a table of physical/chemical constants.

    However, I don't think that formula is what you want. The point of saying that this tank is "of very large area" is that as water drains the height of the water above the hole stays essentially the same. I would suggest treating the water above the hole as a solid falling under gravity. How much water will pass through the hole in unit time?
  4. Nov 24, 2003 #3
    so do I use the formula Q=volume/time?
  5. Nov 24, 2003 #4

    Doc Al

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    Staff: Mentor

    I believe I answered this question in the other forum. Look it up.
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