On Dec 5, 2006, at 1:10 AM, tachyon_1@email.com wrote:

> The Kanakas analogy doesn't hold. In the kanakas, when one ball hits 
> the
> other, the other ball transfers it's energy to the next ball
> and so on until it reaches the end ball which is free to move.

The analogy holds perfectly if the collisions of floors and building
materials are entirely elastic.  I think it doesn't hold if the
collisions are mainly inelastic (in an elastic collision, IIRC,
both kinetic energy of the bodies and their momentum is conserved.
In a perfect inelastic collision, only momentum is conserved, and the
final velocity of the two bodies is equal.  My guess is as good as
yours on where building collapses are on the elastic/inelastic scale,
but you're talking mostly rigid building materials separated by air,
if you account by mass; that sounds pretty elastic (yeah, there's
an energy absorbing factor, but doesn't "rigid" imply that that's
small compared to typical momentums involved?)  In any case, it's
"complicated"; something I doubt that anyone is qualified to predict
from an armchair based on video...

(heh.  Maybe one reason why building implosions are so successful is
because a good part of the procedures undertaken aren't actually
necessary to get a nice collapse...)

BillW
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