Re: car tire friction & contact area

[GJ Schade <gjschade@HOTMAIL.COM>]

> From: Vickie Frohne <VFrohne@BEN.EDU>
> . . . My students enjoy labs where the instructor doesn't know the answer.
> Your
> students might enjoy an exercise where they test the extent to which the
> frictional forces depend on surface area and speed by, for example,
> dragging
> a "standard" wood block across strips of various surfaces, such as aluminum
> foil, rubber shelf liner, a piece of tire tread, etc. etc. . . .

Thanks for the reply, but don't assume those exercises are not already
happening.  My students also enjoy those experiences.  In fact, they figure
out for themselves in lab that surface area and speed do not affect sliding
friction, and that different surfaces and different weights do.  It is in
the discussion of the findings, where the tire question comes up every year.
 Like you apparently, I design as many labs as I can where the students
learn from analyzing experimental data - like "real" scientists.

Greg

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