Re: Coefficient of Friction

[Bernard Cleyet <anngeorg@PACBELL.NET>]

I suppose mu applies to angle of repose also.  Ground  coffee has an angle >
90 deg.

bc

P.s. F, L, & S are slightly off in that section.  ["To make steel ...... if
the melt is cooled rapidly, the carbon precipitates out (sic) in little
grains ....]  Carbon precipitates only if it has a higher concentration than
~ 6.7%.  (At 6.67% there is no iron or carbon it's all iron carbide Fe3C)
Below that steel (actually, with > 2% C is cast iron) is a solution of C and
Fe, and dispersed Fe3C (cementite).  I suspect the authors were thinking of
austenite quenching to produce martensite (supersaturated C in Fe).  To
finish most martensite steels, one heats it (tempers) so the C may diffuse
and form Fe3C (cementite).   This is dispersion (precipitation)
strengthening.  Martensite is too brittle for most uses.  I skipped such
details as, certain tempering will produce e-carbide (C2.4Fe).

I've added another 1%


"John S. Denker" wrote:

> Abul Kalam wrote:
> >



> I just now did an experiment:  fuzzy sock resting on piece
> of sandpaper.  I observed the angle of incline A = 90 degrees
> or more.  Go figure out what mu is.  It's a big number.
> Even if you think this example is too artificial, you can
> pretty easily come up with other examples of seriously
> large static friction.



> Regarding the general topic of strength of materials,
> this is very, very complicated.  If you want 1% of
> the tip of the iceberg, read section 30-7 in chapter
> 30 of volume II of _The Feynman Lectures on Physics_.