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Re: NON-DELIVERY of: Re: Friction -Reply

On Sun, 14 Jul 1996 20:44:25 -0400 said:
It seems to me that if kinetic friction is greater than static friction with
tires, then when your tires started sliding, the increased friction would
cause them to grip again, stop sliding and start turning giving you
breaking action again. A possible indicator that this doesn'r happen is the
tire marks on a racetrack curve. They are all STRAIGHT! If the kinetic

Must have been a strange race. Where I come from the cars go around the curves

friction were greater, the tires turning again would give one control at
least for a limited time and the straight line would be interupted. 'Any

Even as the tires side slip they still turn. It doesn't work too well to
totally lock up the wheels. The tires melt, resulting in substantilly
reduced friction. This is probably what created the straight markes: melted
tires! These guys probably spun and hit the wall. The mu curve has a peak
in it. The idea is to ride as close to the peak as possible. Pass the peak
and it gets interesting in a hurry.

body else think this might be true? The comment made about heating the
tires up by spinning does seem logical to me. It seems possible to have a
kinetic coefficient of hot tires that would be higher that the static
coefficient of cold ones. On the side, if you haven't checked out the
angle where sliding starts with a pair of chaulk board erasers, you may
be very surprised! The tangent of the angle just before slippage is the
value of the coefficient and you'll find it to be VERY high!
Gordon Shepherd

At least if the erasers have chalk on them. Chalk is pretty gritty.
It's no accident that pool players, climbers, and gymnasts use it to increase
friction. You have to be careful to use "real" chalk, which is calcium
carbonate. Some blackboard "chalk" is really kaolinite clay, which is quite
slippery, especially when it is wet. Clay molecules are flat platelets
with charged surfaces that attract water. Chalk is made from microscopic
shells.