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    Re: Need dip-throw a rock?
    From: Tom Sult
    Date: 2011 Jun 22, 21:10 -0500

    For a relatively higher bridge would you expect a larger or a smaller
    error.  I am thinking that the time to push the button is constituent
    and the total time is greater resulting in a smaller error.  If you
    let go a few of those steel balls into the ocean from a hight of say
    30 meter what might one expect?
    Thomas A. Sult, MD
    3rd Opinion
    1415 First First St. South #5
    Willmar, MN 56201
    320 235 2101 Office
    On Jun 22, 2011, at 5:58 PM, Bill Morris wrote:
    > I thought I would discover how well the rock-throwing method might
    > work for me in practice. To avoid discussion about the behaviour of
    > feathers and the shape of rocks, I used petanque balls. These are
    > polished steel balls of 72 mm diameter and weighing 500 grammes,
    > used in the game of petanque (q.v.).
    > I threw them horizontally from the bridge of our ship
    > "Baradozic" ("Little Paradise" in the Breton language - my wife is
    > from Brittany)and used a stop watch reading to 0.01 second to time
    > their fall onto level ground a measured 5.8 metres below.
    > The mean time of 25 throws was 1.29 seconds, with a standard
    > deviation of 0.087 seconds, so that we could expect 95 percent of
    > the times to fall in the range 0.95 to 1.63, as indeed they
    > comfortably did (1.04 to 1.47).
    > Taking the local acceleration due to gravity to be 9.805 metres/s/s
    > gives a height of 8.16, an error of nearly 30 percent. This would
    > give a dip error of 0.8 arcmin.
    > The error is in the right direction. If one assumes a timing error
    > of 0.1 seconds (and you don't have to be old and decrepit to have
    > such an error when operating a stop watch), we get a much closer 6.9
    > metres.
    > The linked photograph shows the bridge of the Baradozic ;-)>
    > Bill Morris
    > Pukenui
    > New Zealand
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