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Fluid Flow in a pipe

  1. Dec 8, 2008 #1
    1. The problem statement, all variables and given/known data
    Use the picture as a guide. P is the pressure in the pipe, and vi is the speed of a non-viscous incompressible fluid at locations i = 1,2,3,4,5.(For each statement select G-Greater than, L-Less than, or E-Equal to).
    [​IMG]

    A) P1 is .... P4
    B) v1 is .... 2v3
    C) P4 is .... P5
    D) P1 is .... P2
    E) v4 is .... v5
    F) P3 is .... P4
    G) v1 is .... v2

    2. Relevant equations
    Bernoulli's Equation p + .5ρv^2 + ρgy
    Continuity Equation: A2*v2=A2*v2

    3. The attempt at a solution
    A) P1 < P4 because P1 has a higher velocity, so pressure must decrease to compensate.
    B) v1 > 2v3, if the diameter is doubled, the velocity is quadrupled as per continuity equation
    C) P4 > P5 due to gravity (ρgy)
    D) P1 > P2 due to gravity
    E) v4 > v5, if v4 has more pressure, it has higher velocity
    F) P3 < P4 due to gravity
    G) v1 > v2, since P1 has a higher pressure it has a higher velocity

    Is my reasoning correct, or do I have something backwards? I guess my main confusion is what effect gravity has on velocity of flow?
     
  2. jcsd
  3. Dec 8, 2008 #2

    Redbelly98

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    Those all look good to me except for E and G.

    What does the Continuity Equation say about the velocities?
     
  4. Dec 14, 2008 #3
    The answers to this question are as follows:

    [Moderation Note: Complete solution removed. Hootenanny ]

    stevebo
     
    Last edited by a moderator: Dec 14, 2008
  5. Dec 14, 2008 #4

    Redbelly98

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    Stevebo,

    Please don't give direct answers to questions, that doesn't help people learn!

    Please read the section on "Homework Help" here:
    https://www.physicsforums.com/showthread.php?t=5374
    In particular:
     
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