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How to find the difference in hieght in a u-tube(Please help)

  1. Mar 25, 2013 #1
    1. The problem statement, all variables and given/known data
    Help! How to find the difference in height in a u shaped tube?
    1. The problem statement, all variables and given/known data

    The horizontal pipe, shown in the figure, has a cross-sectional area of 40,0cm2 at the wider portions and 10,0cm2 at the constriction. Water is flowing in the pipe, and the discharge from the pipe is 6,00∗10−3m3s(6,00Ls). The density of mercury is ρHg=13,6∗103kgm3 and the density of water is ρw=1,00∗103kgm3.
    Find
    a)the flow speeds at the wide and the narrow portions
    b)the pressure difference between these portions
    c) the difference in height between the mercury columns in the U-shaped tube?

    hint(Express the pressure at the lower mercury-water interface in two ways and uzse these expressions to solve for h)

    1 minute ago
    - 4 days left to answer.

    Additional Details
    This is the image of the situation:
    http://session.masteringphysics.com/problemAsset/1260675/1/YF-14-45.jpg
    please can someone help

    2. Relevant equations
    for a) i use AV=volume flow rate
    b)used Bernoullis eqn and made the heights 0
    c) used p=p1 and p=p2+density*g*h

    3. The attempt at a solution
    a) got v at large area=6m/s
    v at constricted area=1.5m/s
    b)got difference in presure to be 16875pa
    c)got 0.127m which is apparently wrong
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 25, 2013 #2

    SteamKing

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    Science Advisor
    Homework Helper

    Shouldn't the velocity in the constricted area be higher than the rest of the pipe?
     
  4. Mar 26, 2013 #3
    Sorry i typed it in wrong they are the other way round
    velocity at the constricted is 6m/s
    velocity at the large is 1,5m/s
     
  5. Mar 26, 2013 #4
    Did you use Bernoulli's equation of flow to get the pressure difference?
     
  6. Mar 26, 2013 #5
    1. The problem statement, all variables and given/known data[/b]
    Help! How to find the difference in height in a u shaped tube?
    1. The problem statement, all variables and given/known data

    The horizontal pipe, shown in the figure, has a cross-sectional area of 40,0cm2 at the wider portions and 10,0cm2 at the constriction. Water is flowing in the pipe, and the discharge from the pipe is 6,00∗10−3m3s(6,00Ls). The density of mercury is ρHg=13,6∗103kgm3 and the density of water is ρw=1,00∗103kgm3.
    Find
    a)the flow speeds at the wide and the narrow portions
    b)the pressure difference between these portions
    c) the difference in height between the mercury columns in the U-shaped tube?

    hint(Express the pressure at the lower mercury-water interface in two ways and uzse these expressions to solve for h)

    1 minute ago
    - 4 days left to answer.

    Additional Details
    This is the image of the situation:
    http://session.masteringphysics.com/problemAsset/1260675/1/YF-14-45.jpg
    please can someone help

    2. Relevant equations
    for a) i use AV=volume flow rate
    b)used Bernoullis eqn and made the heights 0
    c) used p=p1 and p=p2+density*g*h

    3. The attempt at a solution
    a) got v at large area=1.5m/s
    v at constricted area=6m/s
    b)got difference in presure to be 16875pa
    c)got 0.127m which is apparently wrong
     
  7. Mar 26, 2013 #6
    Yes i did you and made the heights 0 because they on the same level.
     
  8. Mar 26, 2013 #7
    I can't see what is wrong with your calculations. They seem legitimate. What are the expected answers for pressure and velocities in your source?
     
  9. Mar 26, 2013 #8
    I don't know that's the problem. I thought it was wrong because someone said that they got this answer and apparently it was wrong but now that you confirmed what I thought maybe he was wrong. Thanks
     
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