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Old 02-21-2007, 11:19 PM   #641
TomW
Dojo: Kodokan
Location: Portland, OR
Join Date: Oct 2001
Posts: 54
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Re: Baseline skillset

Quote:
Erick Mead wrote: View Post
The problem is that even springs are subject to the Third Law. and the reactive push comes from the elastic strain deformations of the structure that the effective "spring" undergoes. An actual spring is just more obvious in its elastic deformation than the more rigid (but still highly elastic) ball bearing. But overloaded springs (of whatever construction) also snap, just as rigid tubes or spheres do.

The question in a resisting mode -- even in linear elastic collisions, which you properly describe -- is determining the limiting load for the structure. True non-resistance does not have that limit, because it never bears a load that would significantly limit it. So it is safer and more effective for doddering old men -- as Ikeda urges us to plan for.
Erick, your physics is on the money. The thing with the analogy and one of the reasons Iggy's is overly simplistic, is that springs, ball bearings, anvils etc. are inanimate objects and the human body is not.

Taking the example of Ueshiba sitting on his rear with his feet in the air and the Sumo tori (not sure if that's the correct term) pushing on his forehead. Ueshiba's rear end is essentially a pin connection with no moment resisting capacity, and he had no bracing system to resist the lateral loading (there's some non-resistance fore you), but he didn't fall over, as an inanimate object would have under the same conditions. So....he either redirected the force vector such that it ran through him, "bounced off the ground" and returned equal and opposite or, he defied the laws of physics with some woo woo ninja tricks. I dunno, but I'm sticking with the physics. Seems clear to me that there's a little more than just waza and the party line "non resistance" going on here.

Just my two cents, YMMV, etc., etc,

Tom Wharton
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