>Kevin and all,
I wrote:
>1. The cross-sectional thickness of a material is proportional to its stiffness.>>
This can be re-phrased more succinctly as, "stiffness is proportional to cross-section".
>Kevin argued
>
>I would disagree with the above. The cross-sectional thickness of a material is not necessarily proportional to its stiffness. In other words, a 10 mm thick steel rod is stiffer than a 10 mm thick piece of pine wood of the same length. Therefore the same cross sectional thickness of these materials are not proportional to their stiffness. However, I would agree that the stiffness of a material is proportional to its cross sectional stiffness. In other words, a 10 mm thick steel rod and a 10 mm thick piece of pine are more stiff than a 1 mm thick steel rod and a 1 mm thick piece of pine.
This isn't very coherent to me? Stiffness is proportional to stiffness? Can't really argue with that, but then its not really useful either?
And if we ask, why is the 10mm steel stiffer than the 10mm wood, I think we would all agree that its because the steel is stiffer than the wood. To reiterate statement 1, above; "The cross-sectional thickness of A material is proportional to its stiffness" (note: A material).
So, I maintain, there is the property of the material, and there is the property of the shape of the structure. The important issue here is that each property can be manipulated separately and each should, therefore, be understood separately.
Of course, its really all a red herring - everyone knows the tendons are the dynamic operators of the MTjt... ;-)
Kind regards,
Stephen
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