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Old 09-20-2007, 08:31 AM   #31
Mike Sigman
Location: Durango, CO
Join Date: Feb 2005
Posts: 4,123
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Re: Aiki-Boxing

Quote:
Timothy Walters Kleinert wrote: View Post
Also, the way I understand whips (and to a lessor extent towels), the reason the wave accelerates is because the whip tapers from handle to tip. Energy is conserved, thus the motion accelerates as the mass of the whip decreases. The human body isn't built this way. Furthermore, a whip can get moving really, really fast. The "crack" of the whip comes from the tip moving faster than the speed of sound, a mini-sonic boom. The human body certainly can't do that.
As in many incremental analyses, you can have several perspectives and analyse a particular phenomenon in terms of forces, levers, momentum, momentum transfer, Impulse, and so on.

What you're saying about a whip is that as you shake a wave down the braided body of the whip, the decrease in diameter of the whip means that velocity must increase as the mass of the whip decreases, because M1V1 = m2v2 (the momentum of a particular mass and velocity must be conserved). Then you say that the human body isn't really built this way, which is true..... but in a way, the body is sort of built like this.

The equation M1V1 = m2v2 can be looked at as the basic explanation of why a billiard ball can roll into another billiard ball and the first ball stops while the second ball begins rolling away. If we make the mass (M1) of the first ball to be twice the mass of the second ball, then the second ball (in a perfect, inelastic collision, neglecting friction, etc.) will wind up rolling away at twice the velocity the first ball arrived with. In a lot of ways, you can look at the torso/middle of our body as the larger first ball and the arm/fist as the smaller second ball. The same transfer of momentum can happen if you connect things up correctly.

Better yet, make it 3 balls. The earth is the first ball, the torso/tanden is the second ball, the arm/fist would be the third ball.

FWIW

Mike
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