Re: Friction

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Sun, 14 Jul 1996, David Dockstader wrote:

> 2.  Max acc is always achieved with some slippage of the tires.  Therefore,
> slipping friction must be greater than static friction.  Drag racers do not
> spin their tires because they are out of control.  They do it because it gives
> the max acc.  Likewise a race car in a turn is deliberately set up to slide.
> Sliding is faster.  To stop the slide you have to slow down!

Just because max acceleration is achieved with slipping tires in some 
situations does not necessarily mean that the coefficient of kinetic 
friction is greater than that of static friction.  Don't drag racers 
simply live with the neccessity of spinning their tires at low speeds 
because their engines won't deliver much power at the low rpm's that 
would otherwise be necessary?

In the case of cornering racers I'm not so sure, but I'm willing to frame 
a hypothesis:  A racer taking a turn at maximum speed with nonslipping 
tires is *just* on the verge of sliding.  Any application of the brakes, 
overapplication of the accelerator, or even *underapplication* of the 
accelerator that results in engine braking will cause the car to go into 
a slide without warning, kind of like trying to run across ice without 
slipping.  Might it be the case that it just ends up being better from a 
control standpoint to allow the rear to break free and use the spinning 
rear tires to help provide a more controllable centripetal force?

Any weekend derby types out there?

John
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