On Sun, 09 Sep 2012 18:02:51 +0100, Grimly Curmudgeon
wrote:

On Sun, 09 Sep 2012 17:15:14 +0100, polygonum
wrote:

but if it wasn't for friction, the wheels would simply spin on the
ground.


T'aint necessarily so. The non-flatness at a macro scale would be
sufficient without any 'real' friction being needed.

Take it small enough and that's all friction is. So, without friction,
you'd be ****ed. We'd all be ****ed.
What's 'real' friction when it's at home?

Sure there are the 'asperities' where the surfaces are imperfectly smooth
- but there are interactions between, say, the tyre and the asphalt which
are at the inter-atomic level.

What was going through my mind was a sort of rack and pinion system - as
if the lumps on the tyres 'fitted' the gaps between projections of the
stones. That would allow movement even if both tyre and road were made of
teflon or even a mythical frictionless material.

--
Rod