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Homework Help: Fluids problem

  1. Jan 13, 2007 #1
    1. The problem statement, all variables and given/known data
    Water is flowing at 1 m/s in a circular pipe. If the diameter of the pipe decreases to four-ninth its former value, what is the velocity fo the water downstream?


    2. Relevant equations

    AV=AV

    3. The attempt at a solution[/b
    (Area1)(Velocity1)=(Area2)(Velocity2)
    then...
    (A1)(1 m/s)=(4/9)A1(V2) ?
    or
    A1=(4/9)(V2)

    Is that right what would u do next??
     
  2. jcsd
  3. Jan 13, 2007 #2
    Rewrite the area in terms of its diameter, and then try again.
     
  4. Jan 13, 2007 #3
    Indeed, remember the area for a circle? *circular* being the key word =).
     
  5. Jan 13, 2007 #4
    couldn't you just with what your given calculate the volumetric flow rate then, then apply Q = AV to get the velocity in the second pipe.. thats how I would do it
     
  6. Jan 13, 2007 #5
    A1V1 = A2V2, since the density is uniform/incompressible.

    You could do as you say, but then you'd have the equation:
    A1 * (delta L1) / delta t = A2 * (delta L2) / delta t

    A1V1 = A2V2 is a better one to use; well more "simple" one.
     
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