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Re: [Phys-l] Another tire question



Thanks, the spokes analogy worked best to explain the tyre function.

Now this reminds me of the problem I had to understand how to add the stretched springs' force constant(s) of a spring oscillator. In my app. the low friction cart is between the springs. When oscillating one spring's tension increases while tother decreases.

bc

p.s. analogously, if the far ends of the springs are not separated the car won't oscillate; if the car is displaced, one spring just flops.

Michael Edmiston wrote:

Brian Whatcott said...


Perhaps a not too unrealistic counter-example will moderate this
idea of "hanging on an upper sidewall/bead."


Well gosh, I think you've described a totally different situation. Rather than the weight being supported by the lower bead and sidewall, I think it is now supported by the air pressure on the bottom of the wheel that is on the bottom only rather than on the bottom and top as in the true wheel. You're example seems like setting a tireless wheel onto a strong-walled balloon. Yep, that ought to work, but it's not the same situation as the tire.

Let me give a counter-counter-example that I think you could probably actually do quite easily, although it won't be real cheap. Take some wire cutters, go to your bicycle, and cut out all the spokes from the top half of the wheels. Get on the bicycle and see if the lower spokes will support your weight.

Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
1 University Drive
Bluffton, OH 45817
419.358.3270
edmiston@bluffton.edu


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