Re: The Olympics

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

If we are not ready to abandon conservation of angular momentum then in the
case of divers and gymnasts either:

1)  They impart some angular momentum into their motion during the jump IF
they clearly have angular momentum ANYTIME during their flight.

2)  There IS enough air resistance to impart a net torque to produce the
angular momentum.

3)  Our eyes get fooled because by moving different parts of the body in
just the right way, the diver/gymnast can reorient their bodies while
maintaining zero angular momentum throughout.

I think that (3) is the solution to the demo that Dewey refers to below.  It
is probably also the solution to SOME of the maneuvers seen done by
divers/gymnasts.  However for other motions (several complete rotations with
all parts of the body moving in the same way) then either (1) or (2) must
hold.  I suspect (1) in most cases.

My $.02

Rick

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Richard W. Tarara
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

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----- Original Message -----
From: "Dewey Dykstra, Jr." <dykstrad@EMAIL.BOISESTATE.EDU>
> > ....  Only stroboscopic pictures would reveal
> > the truth.
> > Zach
>
> Actually a force plate or table would be very useful too in order to
> detemine the magnitude and direction of the force applied by the athlete
to
> the surface from which they are springing.
>
> While it is not always well transmitted to the athletes by coaches and
> judges, most physical education depts have changed names to things like
> Kinesiology and many faculty in these depts make as careful studies of
> these motions and the human bodies concerned as any one in any of the
> science depts.  Their work is published in journals (if memory serves one
> of the major ones is The Research Quarterly) and books (James Councilman's
> book The Science of Swimming is quite good on the physics of the major
> competitive strokes).  You should be able to find these in most university
> libraries.
>
> Also, on the cats, a NASA astronaut was interested in figuring out how his
> cat accomplished the feat of landing on its feet.  There is some footage
> from NASA on this.  In particular Bob Fuller and I worked on a project
> called Physics Vignettes originally published by John Wiley and Sons on
> tape and videodisc.  It is now available from ZTeck on CD-ROM.  I believe
> there was a vignette Bob worked on involving the NASA footage and then an
> experiment with divers over a pool attempting to switch from a vertical
> head up to a vertical head down position during a vertical fall.  They did
> not leave from a board or platform but started hanging by their hands
above
> the pool and attempted to enter the water vertical but now hands down and
> feet up.  It can be done.
>
> Dewey
>
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> Dewey I. Dykstra, Jr.                 Phone: (208)426-3105
> Professor of Physics                  Dept:  (208)426-3775
> Department of Physics/MCF421/418      Fax: (208)426-4330
> Boise State University            dykstrad@email.boisestate.edu
> 1910 University Drive                 Boise Highlanders
> Boise, ID 83725-1570                  novice piper: GHB, Uilleann
>
> "As a result of modern research in physics, the ambition and hope,
> still cherished by most authorities of the last century, that physical
> science could offer a photographic picture and true image of reality
> had to be abandoned."  --M. Jammer in Concepts of Force, 1957.
>
> "If what we regard as real depends on our theory, how can we make
> reality the basis of our philosophy? ...But we cannot distinguish
> what is real about the universe without a theory...it makes no sense
> to ask if it corresponds to reality, because we do not know what
> reality is independent of a theory."--S. Hawking in Black Holes
> and Baby Universes, 1993.
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++