It seems to me the girlfriend-gymnast has contradicted herself and has
affirmed those who state the athlete leaves the ground with angular momentum
when she states, "it is possible to decide which way to twist AFTER leaving
the ground." If a person sometimes has to twist one way and sometimes twist
the other way, in order to accomplish the same maneuver, and she decides
this after leaving the ground, how else can we interpret this other than she
is compensating for slight differences in launch dynamics. Her perception
may be that she is not imparting angular momentum at launch. But her
statements are consistent with the fact she is imparting angular momentum at
launch and she has to compensate during flight for slight excess or deficit
of angular momentum created by inconsistencies in the launch.
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817
Zach Wolff said:
There seems to be general agreement from list members
that divers and gymnasts either leave the ground or
board with some angular momentum or perform
complicated gyrations, moving one half the body then
the other, to execute a mid-air twist. My girlfriend,
a gymnast, argues that this is not so. She claims
that it is important to leave the ground with no
rotation whatsoever and that move required to twist is
simply to draw both fists to the one shoulder and turn
the head toward that same shoulder, causing a rotation
in that direction. I am unable to understand how this
could possibly cause the rotation in the intended
direction. It is possible that her intuitions are
incorrect. Only stroboscopic pictures would reveal
the truth. However, her argument is strengthened by
two factors: one, she claims that leaving the ground
with any rotation leads to a point deduction and
judges are watching very carefully, two, she claims
that it is possible to decide which way to twist AFTER
leaving the ground. She makes the same claims for
diving where she has some experience, but not at a
competitive level. Can anyone make sense of this
data?