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Homework Help: Velocity of a water jet given water pressure and diameter?

  1. Oct 15, 2008 #1
    I need to determine the velocity of a water jet. For example, if a garden hose is 1/2" in diameter and we assume that the water pressure is 40psi, what would be the water velocity (in ft/s) as it exits the hose (assuming no nozzle)?

    We know Pressure = force/area, but I want to know the velocity in feet/second, so I don't know what equation to use!

    Since velocity has a time component, would we need to introduce another factor? Maybe estimate the gallons per minute? Is this known for a typical garden hose? Thank you in advance!
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 15, 2008 #2


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    You can estimate flow speed from an orifice given just it's size, the presure and a factor that describes the shape.
    Have you tried looking up orifice+flow in your textbook.
  4. Jun 28, 2011 #3
    .32 X GPM
    _________ = Ft/Sec velocity
    TFA (sq. in.)
    http://www.uiweb.uidaho.edu/extension/lawn/Files/Garden_Hose.htm [Broken]
    Last edited by a moderator: May 5, 2017
  5. Jun 28, 2011 #4
    Use the Newton's second law, considering a small dt amount of time.
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