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Unread 15-12-2008, 07:27
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Re: HDPE or ICE FLOOR

Quote:
Originally Posted by EricH View Post
Namely, surface area doesn't matter.
This isn't _entirely_ true. In an ideal physics world, yes, but there are cases where surface area is proportional (or inversely proportional) to grip.

-Racing cars have very large, wide tires (even though this increases unsprung weight) because it means that if the tire hits an imperfection in the track, it doesn't lose grip. Since the track is always imperfect, this has the effect of effectively very slightly raising the car's coefficient of friction (although the ideal rubber-on-ashphalt coefficient remains the same)
-Skates have very little surface area because it takes a lot of pressure at the skate-ice interface to create the microscopic layer of ice that the skate glides on.

Likewise, I'm not sure the rubber-on-carpet case is a cut-and-dry Ff = uFn case. It might be like Velcro: if you have two big sheets together, it is much harder to pull one off sideways than if you have two small sheets together. Despite the normal force being the same, it takes much more force to move the two sheets relative to each other when there is more surface area in contact.

There have probably been some teams that have done tests, it would be interesting to see the results.
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