Since the list did so well on the water-displacement/painted cylinder
questions, maybe you can help me out on one that my Dynamics profesor
asked us about eight years ago. I still haven't found a definitive
answer. It IS automobile-related, but not necessarily LBC.
First, some background information: The coefficient of friction
between to surfaces does not rely on the amount of surface area in
contact, only on the weight of the object being moved. This is why a
tall, skinny box is not any easier to slide across a floor if you
have the small surface in contact with the box than if you have the
big side in contact with the floor. This is true whether you're
talking about sliding friction or static friction. (sliding friction
is the box sliding across a floor, static friction is like a wheel
rolling across the floor--no points on the floor and wheel ever
actually slide relative to one another, but there's still friction,
also known as rolling resistance).
Here's his question. If the coefficient of friction is only
dependent on the two surfaces in question and the weight of the
object being moved, and not the amount of surface area in contact
with the ground, why do drag racers use such wide tires? Discount
anything having to do with cornering, since drag racers are just
interested in straight-line movement. Those of you who still
remember any dynamics classes you may have had can do the math
yourself--On paper, a car should be able to generate the same
forward force whether it is fitted with bicycle tires or 30" wide
Mickey Thompson Slicks, as long as the rubber used in both tires is
the same, and the weight of the car remains the same.
I have an idea, but I don't want to prejudice the list.
I'll post my hypothesis for confirmation or ridicule in a day or two.
Scott
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