🚀 go-pugleaf

In article <45ha8i$cff@dscomsa.desy.de>,
   vanesch@dice2.desy.de (Patrick P. E. Esch) wrote:
>Glenn Proctor (proctor@yorvic.york.ac.uk) wrote:
>
>: I have a friend who is interested in the biomechanics of body
>: movement, with particular emphasis on punching etc in karate.
>
>: The techniques used are often described as being "like a whip" but 
as
>: yet we have found no concise, comprehensive description of 
precisely
>: how a whip works.
>
>Having done some karate myself (and having the ambition to continue 
:)
>I guess what they are referring to is this technique of first making
>a movement with your hips a fraction of a second before the arm is
>pushed out in a straight line to the target.  Personally it made me
>think of a running wave, starting from your hips and going over your
>shoulders into your arm and finally in your fist.  As the masses of
>these things (hips, shoulders, arm, fist) decrease, and increasing
>acceleration (I guess to keep about the same energy in the wave 
crest)
>is observed, with the fist hitting the target very hard.  It takes
>a while before one learns to synchronise these movements correctly,
>but once one does it right, the effect really shows.
>Perhaps a whip is based onto the same idea of letting a transverse
>wave run through material with decreasing mass per unit length, but
>that I don't know.
>
>cheers,
>Patrick.
>

Yes.  A pulse of a given energy travels toward the tip of a whip, 
where it gets thinner and thinner.  Properly tensioned, the pulse 
continues without too much energy dissipation (yet!).  Since the whip 
gets thinner, the pulse causes each consecutive small section of whip 
to move up and down faster and faster, to conserve energy.  In 
bullwhips, for example, the motion at the tip can be so fast that it 
goes supersonic, resulting the familiar *CRACK*.


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Marty Schleehauf                            To hear is to forget,
Professional Engineer                      To see is to remember,
IRC /nick "tau" or "au"                   To do is to understand.