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Homework Help: Fluid physics help

  1. Jan 14, 2009 #1
    1. The problem statement, all variables and given/known data

    Water flowing out of a 16-mm diameter faucet fills a 2L bottle in 10s. At what distance below the faucet has the water stream narrowed to 10mm diameter?

    2. Relevant equations

    A1v1=A2v2 Q=vA

    3. The attempt at a solution
    edit: this is what I TRIED to do:(*note: i ignored some unit conversions at this time)

    Q=2L/10s=2x10^-3 m^3/s.

    v= Q/A = 2x10^-3 m^3/s / pi(5mm)^2 = 2.54x10^-5

    x=vt = 2.54x10^-5 * 10s = 2.54*10^-4.
    lol this is so wrong, it doesnt make any sense.
     
    Last edited: Jan 14, 2009
  2. jcsd
  3. Jan 14, 2009 #2

    LowlyPion

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    Homework Helper

    Re: Fluids

    The presumption is that as the water falls it will narrow because of it's increase in speed?

    Calculate the velocity of the water coming from the opening - 2 liters flowing through the area of the opening in 10 seconds - and then figure what velocity will be required to flow through an area that is reduced to 10 mm. That velocity should occur from gravity at v² = Vo² + 2 g*x where x is the distance below shouldn't it?
     
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