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Find difference in pressure in this water intake pump

  1. Apr 21, 2006 #1
    A water intake at a pump storage reservoir (Fig. 14-44) has a cross-sectional area of 0.87 m2. The water flows in at a speed of 0.35 m/s. At the generator building, at distance D = 180 m below the intake point, the cross-sectional area is smaller than at the intake and the water flows out at 9.8 m/s. What is the difference in pressure, in megapascals, between inlet and outlet?

    Im using Burnoulli's Equation:

    P1 -P2 = density(g)(Y1- Y2) + 1/2 (density)(V2^2 - V1^2)
    density of water = 1000
    so = (1000)(9.8)(180) + 1/2(1000)(9.8^2 - 0.35^2)
    = 1811958.75Pa/1.01x10^5Pa
    = 17.94 atm

    But then answer is in MPa, So then i get 1.794 x10^-6 MPa

    But that is not correct, is the analysis i made incorrect? I think i am missing something key in the problem. Thanks in advance.
  2. jcsd
  3. Apr 21, 2006 #2


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    Science Advisor

    Without looking at your problem set up your conversion from atm to MPa is incorrect. 17.9 atm = 1.81 MPa.
  4. Apr 21, 2006 #3
    Why did you convert from Pa to atm? Just convert Pa to MPa.
  5. Apr 21, 2006 #4
    to be honest, im not sure i did. silly.

    but is the analysis i did correct for the problem?
  6. Nov 24, 2008 #5
    Re: Pressure

    Did he do the question correct?
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