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Re: Friction



I quite agree with you.

Roger

If you listen to the commentary on TV about drag racing, you might be
led to the idea (as I have been) that the reason for the 'burn out'
before the race IS to put down a layer of rubber on the track at the
start area. The rubber does melt off the tires and coat the surface
but then quickly solidifies. Presumably, the rubber to rubber
friction is greater than the rubber to asphalt friction. The warm
tires are also softer. HOWEVER, it is also VERY clear from watching
the races, that in the actual race ANY slippage (spinning) of the
tires is the kiss of death to the racer. This causes them to lose
traction and they normally just shut down the engine at that point.
During the race the tires MUST roll for maximum performance.

Rick Tarara
----------
From: PHRP@FHSUVM.FHSU.EDU

A student into drag racing once told me that the reason for spinning
the tires
is to heat up the rubber so that it begins to melt and thus "flow"
into the
surface of the pavement. This increases the frictional force between
tire and
pavement.

What is happening is that by heating the tire by causing it to spin
on the
pavement, the driver is changing the material and hence the
coeficient of
friction between the tire and the road. The hot tires behave
differently than
cold tire rubber. In Dr. Shapiro's example, and that is true for the
rest of
us, we start to skid because the tire is not rolling, and the
coeficient of
friction in the skid is less than if we allow the tire to roll.
Passenger car
tires are of a different rubber than racing tires. Antilocking
brakes are
based on the idea that we maintain the greatest coeficient of
friction between
tire and road by allowing the tire to roll--NOT slide.