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Maths question that stumped me

  1. Nov 3, 2006 #1
    I have a maths assignment for aquaculture that is due in on monday and this one questions has stumped me:

    if a system which contained 2998cubic litres at full capacity was filled from an ocean intake pipe that was 200m long and 100mm wide and delivered water at a velocity of 3 ms-1, how long would it take to fill the system to capacity?

    can any one help?
  2. jcsd
  3. Nov 3, 2006 #2


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    Assuming the pipe is cylindrical in shape and that d=100mm is its diameter, then there is in the pipe [itex]\pi(d/2)^2[/itex] cubic meter of water per meter of lenght. And the water is flowing at v=3m/s in the direction of the lenght. So water is poured into the tank at a rate of [itex]\pi(d/2)^2v[/itex] (m³*m)(m*s)= [itex]\pi(d/2)^2v[/itex] m³/s.
  4. Nov 3, 2006 #3


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    Well it's not a good question because they don't tell you that the pipe delivers its full capacity of water for the entire filling process. But beyond that, it doesn't make much sense because they give you the length of the pipe, which doesn't seem to factor into the question.

    The length may be just to confuse you, or it may be that you must assume the water takes 200/3 seconds to fill the pipe before filling the tank. I think this is stretching the imagination a bit far though.

    Assuming the length was just a decoy, you determine how much water will be provided per second, and then you can use that to determine how many seconds it will take.

    Since 3m/s of water is delivered, you must calculate how much water fits in 3 metres of pipe (a cylinder with height 3m, diameter 0.1m).
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