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Homework Help: Velocity of fluid in venturi tube

  1. Feb 19, 2015 #1
    1. The problem statement, all variables and given/known data
    A venturi tube is a means of measuring fluid velocity. One particular device consists of a level, circular pipe of radius 5.7 cm which at one point narrows to a radius of 3.7 cm. An ideal, incompressible liquid flows through the tube and the pressure difference between the wide and narrow parts is found to be 3.5 kN/m^2. If the density of the liquid is 1120 kg/m3 what is the velocity of the fluid in the wide part of the pipe?
    ρ = 1120 kg/m^3
    ∆P = 3.5kN/m^2
    narrow radius = 3.7cm
    wide radius = 5.7cm

    2. Relevant equations
    Continuity: ρA1v1 = ρA2v2
    Bernoulli: P + 1/2ρv^2 + ρgh
    3. The attempt at a solution
    I tried finding v1 by using the rearranging Bernoulli's equation v = √((2∆P)/ρ) = 2.5m/s
    Then using continuity equation, tried to find v2 which happened to equal 1.05m/s. Incorrect.
    Last edited: Feb 19, 2015
  2. jcsd
  3. Feb 21, 2015 #2


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    Homework Helper

    You need the Bernoulli equation. What you wrote it was not an equation.
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