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Physics Buoyancy Problem

  1. Dec 12, 2012 #1
    1. The problem statement, all variables and given/known data


    Consider a hose that carries water (density = 1000 kg/m3) leads to a nozzle that is elevated h = 1.3 meters above the ground. The nozzle has a diameter d, and the hose has a diameter D = 5d. Water flows through the hose with a speed vH = 0.6 m/s.

    (a) What is the speed of the water as it leaves the nozzle?

    (b) What is the gauge pressure of the water in the hose at ground level?

    2. Relevant equations

    P+pgh+(1/2)pV^2 = P+pgh+(1/2)pV^2
    Area * V = Area * V

    3. The attempt at a solution
    I'm confused on the part where the hose is elevated upward, I know the velocity decreases, but I don't know by how much.
  2. jcsd
  3. Dec 12, 2012 #2


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    Staff: Mentor

    Is water compressible or incompressible? What does that imply for the flow rate at any point along the (constant diameter) hose?
  4. Dec 12, 2012 #3
    It is compressible, does that mean it stays the same throughout?
  5. Dec 12, 2012 #4


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    Staff: Mentor

    Are you guessing? If water is compressible, why can't we store a cubic meter of water in a one liter container? :smile:

    For all practical purposes, water is NOT compressible. So for a filled, constant diameter pipe, the flow rate must be the same everywhere -- otherwise, wouldn't water "pile up" behind the slow regions and "thin out" in the speedy ones?
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