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Homework Help: Help using Bernoulli's equation

  1. Nov 23, 2009 #1
    1. The problem statement, all variables and given/known data

    Water flows at 0.61 m/s through a 3.0 cm diameter hose that terminates in a 0.30 cm diameter nozzle. Assume laminar non-viscous steady-state flow.

    (a) At what speed does the water pass through the nozzle? (Correctly solved to be 61 m/s).

    (b) If the pump at one end of the hose and the nozzle at the other end are at the same height, and if the pressure at the nozzle is 1 atm, what is the pressure at the pump in atm?

    2. Relevant equations

    P1 + .5p(v1)^2 = P2 + .5p(v2)^2

    P1 = Looking for this
    p = 1000 kg/m^3 ??
    v1 = .61 m/s
    v2 = 61 m/s
    P2 = 1 atm

    3. The attempt at a solution

    I plugged in all known variables, but P1 ended up being a very large number (1860314.95 atm), and this was incorrect. I'm thinking that possibly the density that I'm using is incorrect. Can anyone see what I am doing incorrectly?
  2. jcsd
  3. Nov 24, 2009 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Most of your quantities are in metric (MKS) units, so the pressure will have to be converted to those units first.
  4. Nov 24, 2009 #3
    Thanks! I wasn't sure about those units either.
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