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    From: Fred Hebard
    Date: 2003 Dec 26, 09:36 -0500

    Not being a physicist or engineer, resonance is not a subject with
    which I am strongly conversant, and I finally came up with an example
    that might be helpful to the similarly challenged.  My example is a
    "Slinky", which is a tension spring about 5-cm diameter, about 5-cm
    long compressed, stretching out to about a meter, sold as a toy in the
    U.S.  "Slinkys" can be made to walk down stairs and do other fun
    things.  If you hold one at the end and let it drop, a slight upward
    flick at just the right moment with cause it to spring back up toward
    your hand, whereas a similar flick at another moment has almost the
    opposite effect, dampening the spring action and causing it to dangle
    from your hand, with no satisfying spring back.  I expect the flick
    that causes the Slinky to spring back to your hand is in phase with the
    natural resonance of this system, while the worst example of the other
    flick is one-hundred eighty degrees out of phase.

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