Re: [Phys-l] Another tire question

[John Denker <jsd@av8n.com>]

On 11/07/2007 03:21 PM, Rick Tarara wrote:

> If the tire is sitting on the ground--no wheel involved--we would not split 
> it in two.  We would say that the ground pushes up on the tire.  When I 
> stand on the floor, the floor pushes up only on my feet, but we say that the 
> floor pushes up on me.  We resort to tension/stiffness/compression and the 
> like to explain how these contact forces are 'distributed' over all parts of 
> the object.  I guess my concern here was--why consider the tire in halves 
> and not thirds, 10ths, or whatever.  Why are we isolating the effect of the 
> ground to the lower half and not distributing it to the whole tire



Any serious analysis would consider at *least* ten sectors,
dividing up the azimuth.

However, at the level of an "Introduction to Practical Physics"
course, analyzing only the 12:00 sector and the 6:00 sector
gives the flavor of what's going on, to first order.  

The second-order things are treeemendously more complicated.