Discussion of the Question 06/04
THIN ICE
The question was:
Why can a person run on thin ice (over a pond), but cannot stand on
it?
(9/04):
Sam Crown from Gresham, Oregon, USA (e-mail
samcrown@earthlink.net)
sent us an email correctly identifying the reasons for thin ice supporting
the runner. He wrote:
The non-compressible water beneath the ice has to flow away from the
area under the runner's feet before the ice can bend. Given the inertial
and viscous nature of the water, this flow process isn't instantaneous;
if the load applied beneath the runner's boots is quickly applied and
released, the ice won't deflect enough to fail. When the runner stops,
the water beneath the ice flows out from under his feet and the ice bends
and breaks.
Can we make this solution more quantitative?
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