Re: pinhole Car on Ice

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From: Gene Thompson (gthompso@ccsf.cc.ca.us)
Date: Sun Nov 12 2000 - 12:07:35 PST 

Date: Sun, 12 Nov 2000 12:07:35 -0800 (PST)
From: Gene Thompson <gthompso@ccsf.cc.ca.us>
Subject: Re: pinhole Car on Ice
Message-ID: <Pine.HPX.4.21.0011121205390.10522-100000@fog.ccsf.cc.ca.us>

What is the advantage (if there is one) of the shape of the blade on ice
skates, then? With the traditional explanation, it was that the entire
weight of the body was consolidated onto one thin edge (and you can really
feel it through the soles of your feet) but, if you don't need the
pressure to melt the ice, is the current skate design the best? What
would work better and why?

Ellen Koivisto
George Washington High School, SF

On Sat, 11 Nov 2000, Paul Doherty wrote:

> Hi Jhumki
>
> Ice is frictionless because the top twenty layers of water molecules in
> solid ice behave like a liquid in their structure and properties. These
> molecules easily slide over each other. So even if the rubber of the tire
> sticks to the top layer of water molecules, these molecules slide over the
> ones below just as they would in a liquid.
>
> (This is the new theory of how ice skaters skate too, the old myth that the
> pressure of the skate blade melts the ice is now known to be wrong. Water
> ice will melt under pressure but the pressure at the skate blade is too low
> by more than an order of magnitude.)
>
> Paul D
>
> Paul "But it is more complicated than that!" Doherty,
> Senior Staff Scientist, The Exploratorium.
> pauld@exploratorium.edu, www.exo.net/~pauld
>
>
>
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