Re: Friction

[palmer@sfu.ca (Leigh Palmer)]

> I'm still looking for stuff that will show greater forces for kinetic friction,
> variation with area, and variation with speed.

I'm told that ground cast iron on PTFE (Teflon) works this way. Telescope
mountings must not exhibit stick-slip phenomenon. Large telescopes are
sometimes floated (e.g. on mercury) or have pumped oil lubricated bearing
surfaces to avoid it. The increased kinetic friction is simply ascribable
to viscous dissipation in those cases, and for low speeds the frictional
force is proportional to relative velocity. I suppose one needs a new term
(and formula) for that phenomenon, too, by current pedagogical standards.
It is certainly a common one in nature and technology. How could we have
overlooked it?

You may say that we just don't want to confuse students by introducing too
much. I say that is not correct; we teach the conventional because (as
Professor Irwin Corey used to say) "It's in the Book!"

Well, folks, I'm here to tell you that we *are* confusing the students!
Before I retire I'd like to learn why, so we all can stop doing it.

Leigh