Posted by: Jack Mankin (MrBatspeed@aol.com) on Fri Mar 22 00:08:49 2002

Hi Major Dan

I have read “Volume 10. Physics 208” before. The first 2 paragraphs below are taken from “Volume 10 of Physics 208”
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Whip Action

“The flicking of a towel in the shower room is a long tradition to make a very high speed hit that stings. The buggy whip tip gets so fast that the tip exceeds the speed of sound and makes a sonic boom! In our PoS book, we have a rather good discussion of the physics of fly casting by Robson, on p 304. The basic principles of the physics of the whip can be found here.”

Whip action as applied to the golf or baseball strike.

In the golf swing and the baseball swing, a rather similar thing happens. The club or bat trails the hand so that the hand. With the reduced moment of inertia, the hands driven by the large muscles of the legs, hips and trunk obtain a larger velocity. When the hands are slowed down, the energy stored in the entire system is transmitted to the smaller mass segmenets until the club [bat] take on most of the kinetic energy and since they are less massive, they have a high velocity.”
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This is the same concept described by Professor Adair in his book, “The Physics of Baseball” (he may have authored this article as well). It contends that it is the transfer of "kinetic" energy (energy stored in the entire system) that accelerates the bat-head as the hands slow down. Adair believes the “system” developed the kinetic energy from the “linear” movement of the batter’s mass. He stated that the body moving forward about 18 inches at 6 or 8 mph develops the kinetic energy that powers the swing.

I wrote Professor Adair that my study of the swing found the forward movement of the body ceases before the initiation of the swing. That during the actual swing, the body rotates around a stationary axis, and it was the transfer of the body’s rotational momentum that accelerates the bat by the angular displacement of the hand-path and torque applied (not the linear acceleration of the hands). --- After a few unflattering comments, he ended his reply by writing; “I found your essay on batting quite unpersuasive even as it was non-quantitative. And any batter who would use your “stationary axis” model, taken literally, could not hit a ball past second base.” --- Adair also discounts torque (push/pull of hands) as a factor in generating bat speed.

You can generate get a good “snap” with a towel (whip effect) from the quick linear extension of the hands. But you will not get those results with a stiff bat. That is what I proved with the test shown in the instructional video with the “steering wheel knob” attached to the bat. – There are no smaller mass segmenets in a bat like in a towel or whip – in fact, a bat’s mass increases down its “stiff” length.

Jack Mankin