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    Re: Wind & Current Navigation
    From: Dan Allen
    Date: 2003 Apr 17, 14:57 -0700

    On Thursday, April 17, 2003, at 02:08 PM, George Huxtable wrote:
    > Now for Dan's fair question: why the square?
    > Let's consider something like a dustbin-lid on a long bridle, towed far
    > behind an immersed submarine. It makes no difference whether it's the
    > bin-lid moving through the water, or a water-current impinging on the
    > lid.
    > If the speed doubles, then in a given time twice as much water
    > impinges on
    > the lid. And with the speed doubled, every drop (or every molecule or
    > every
    > gram) of that water has twice as much momentum (which is mass x
    > velocity)
    > which it gives up to the lid when it's brought to a stop. Force is
    > given by
    > the rate of transfer of momentum, so we get the force increased by 2 x
    > 2 =
    > 4. Is that good enough to satisfy Dan, or does he wish to get more
    > fundamental?
    More fundamentals!  Teach us hydrophysics!

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