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Bernoulli's principle

  1. Oct 7, 2012 #1
    1. The problem statement, all variables and given/known data
    Please click on the following link for the solution.

    http://s1292.photobucket.com/albums...ew&current=Bernoullisequation_zps0d4485d7.jpg

    2. Relevant equations

    P1 + .5(rho)v12 + (rho)gy1 = P2 + .5(rho)v22 + (rho)gy2


    3. The attempt at a solution

    P1 = 101300 Pa
    y1 = 0
    rho = 1015 kg/m^2
    v1 = 0.1*10^-2 m/s
    P2 = ?
    y2 = 2.0 m
    v2 = 0.5 m/s

    Plugging numbers into bernoulli's principle

    P2 = 101300 + .5(1015)(0.1*10^-2)2 + 0 - .5(1015)(.5)^2 - 1015*9.8*2
    P2 = 81281.66Pa

    But according to the textbook, the answer is 120,800 Pa. I get that answer when y1 = 2.0 and y2 = 0. I don't understand how the reference height could be at P2 could be at 0 because if it was, shouldn't P2 be denoted as P1?

    Any help would be appreciated.
     
  2. jcsd
  3. Oct 7, 2012 #2
    The height at the manometer is two meters LESS than the height at the beer level. No matter what you use as the reference height, y1 - y2 = 2 m.
     
  4. Oct 7, 2012 #3
    So for this question, the reference height of 0 is already set at the manometer? Is it possible to use the reference height at the beer level in the container?
     
  5. Oct 7, 2012 #4
    As I said, the "zero" level can be anywhere, but you must have y1 - y2 = 2 m.
     
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