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Homework Help: 15.6 pressure in a pipe

  1. Apr 10, 2007 #1
    1. The problem statement, all variables and given/known data

    Water flows at through a horizontal pipe that narrows smoothly from 10 cm diameter to 5.0 cm diameter. A pressure gauge in the narrow section reads 50 kPa.

    What is the reading of a pressure gauge in the wide section

    2. Relevant equations


    3. The attempt at a solution

    I tried to use this equation and it didn't work. I already know the answer is 5.34 x 10^4 but I need to know how to get that answer.
  2. jcsd
  3. Apr 10, 2007 #2
    Do you know bernoulli's eqn. I think that is what is needed here. Hint: in the narrow section the water must have 4 times the velocity as in the wide section. I'm off for now but maybe others can pick up if you need additional help.
  4. Apr 10, 2007 #3
    Let me see if I have the equation correct.

    P1-P2=1/2 (density) (V2^2-V1^2)



    Is this what you are talking about?
  5. Apr 10, 2007 #4


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    Gold Member

    Yes. Those are correct. You can see the derivation here -

  6. Apr 10, 2007 #5
    Thanks for your help this make sense now
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