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Homework Help: Solids and Fluids: Time

  1. Apr 11, 2010 #1
    1. The problem statement, all variables and given/known data

    SAE no. 10 oil has a viscosity of 0.2 Pa· s. How long (in sec) would it take to pour 4 liters of oil through a funnel with a neck 10 cm long and 2.9 cm in diameter. Assume that it is poured in such a way that the oil level is kept just above the top of the tube.

    Hint: The specific gravity (= ratio of its density to that of water) of the oil is 0.70.

    3. The attempt at a solution

    Dp = rgL
    = (700 kg/m3)*(9.8 m/s2)*(10*0.01 m) = 686
    The fow rate is given by Poiseuille's law:
    Q = p r4 Dp / (8 h L)

    => t = V / Q = 8 V h L / (p r4 Dp) = 8*(4*10^-3)*0.2*(10*0.01) / (700*(0.5*2.9*0.01)^4*686 = 0.03 s = wrong answer.

    Please advise! Thanks!
  2. jcsd
  3. Apr 12, 2010 #2
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