Kinetic friction vs static friction?

[short_tarts]

OK, so in my physics class we are doing friction. And the book states that static friction usually larger then kinetic.
Then he posed a question to whether or not there might be some crazy scenario where the kinetic friction is larger than the static friction?
Personally, I cannot think of anything.


I thought it would make for some interesting discussion and maybe some enlightenment.
Any other takes on this?

 

[nnnm4]

I'm pretty sure rubber has some interesting friction properties...I'll look into it.

 

[KLoux]

Yeah, I'd look into rubber. Have you ever seen plots for the forces created by a pneumatic tire? If you look at the longitudinal forces (think drag racing - acceleration in a straight line), then there is an optimal amount of "slip" where you will get the highest coefficient of friction. In the industry, they don't usually use the terms "static" vs. "kinetic" friction (only useful if you are trying to determine the slope of a hill where your car couldn't park because it would slide down, for example - not a realistic/useful problem to solve).

So I don't know if rubber has a larger coefficient of dynamic friction than static friction, but it does have some interesting friction properties and I wouldn't be surprised to hear that this is true...

-Kerry