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Justin Penrose
09-01-1997, 03:29 AM
I am trying to track down information on the concept of "Effective
Striking Mass". I am reading "Neuromechanical Basis of Kinesiology" by
Robert Enoka, 2nd Ed. and on page 97 there is a curious passage which
goes unreferenced:

"The critical variables affecting velocity after collision as the
coefficient of restitution, the velocity before contact, and mass.
Whereas the above example used the actual mass of the ball and the bat,
the mass of the bat may be larger due to Plagenhoef's concept of the
effective striking mass. There does not seem to be any information
available on whether the mass of the baseball bat is supplemented due to
its connection to the rigid links of the athlete."

I understand that if one was to simply throw the bat at the ball there
is a collison in the classical sense. However, a batter tends to
"throw" him/herself along with the bat and "collide" with an oncoming
pitched ball. In addition, I understand that forces applied to the grip
accelerate the bat into the oncoming pitch, however, at the moment of
impact if one is "limp wristed" with the bat moving quickly the results
of the collision is less effective than if the one is stiff wristed with
the bat moving quantitatively slower.

--
Andrew S. Bonci, BA, DC, DAAPM

An intersting one this one, and I would be interested to hear the thoughts of other members.....
However, I got the impression from some articles that since the duration of the impact was small in baseball (about 1ms or less), the bat can only behave as a free unconstrained body during that time. (the reason was something about not enough time for sound waves to travel to the handle and back and thus be effected by the hands). Thus, the 'grip' was irrelevant and the post-impact ball velocity was only effected by the bat's flexure properties, mass/linear/angular velocity at impact, and other Hertzian-like contact parameters.

What does anyone else think?

Justin Penrose
Medical Physics
University of Sheffield