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Homework Help: Fluid Dynamics

  1. May 27, 2010 #1
    1. The problem statement, all variables and given/known data
    A fire-hose must be able to shoot water to the top of a building 35.0 m tall when aimed straight up. Water enters this hose at a steady rate of 0.500 m³.s¯¹ and shoots out of a round nozzle.

    (a) What is the maximum diameter that this nozzle can have?

    (b) If the only nozzle available is twice as great, what is the highest point that the water can reach?

    2. Relevant equations

    flow rate = pir^2 x h/1

    3. The attempt at a solution

    (a) 0.5 = pi r^2 x 35 / 1
    r = 0.067m

    (b) 0.5 = pi x 0.134^2 x h/1
    h = 8.86m

    Can someone please check I am doing this correctly. Thanks!
  2. jcsd
  3. May 28, 2010 #2


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    Homework Helper


    If your volume is V=πr2h and you divide throughout by time t to get flow rate Q

    you will get Q=πr2(h/t)

    h/t is distance per unit time which is velocity.

    so you have Q=πr2v

    you need to get v from the fact that the height the water must reach is 35m.
    Last edited by a moderator: Apr 25, 2017
  4. May 28, 2010 #3
    Thanks Rock freak... did this too quick without thinking much! All good now.
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