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Re: [Phys-l] expand your mind



Spagna Jr., George wrote:

I suspect that the dough on the outer circumference is stretched more
nearly to its elastic limit, while that on the inner circumference (i.e.
surrounding the hole) is not. Raising the pressure "inside the balloon"
causes a greater displacement of the inner edge than the outer.

Oooh, I like it. It is easy to imagine an inelastic "skin"
forming on the dough, due to uneven drying, or uneven loss
of CO2 during rising.

Experimental test, similar in spirit to John's "freely suspended" model:
make an assortment of disk and hemispherical shapes from dough, watch
them rise and measure whether the locus of greater expansion correlates
with the locus of smaller radius of curvature.

And/or: nick the outer edge of the dough with scissors, to give it some
extra length to play with, as illustrated in this figure:
http://www.av8n.com/physics/img48/bagel.png

If the outer perimeter is under tension, the nicks will "pull open" to
some degree.