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Re: [Phys-l] The "why" questions



On 11/25/2010 10:21 AM, ludwik kowalski wrote:
/snip/ the "why" questions are often asked by students, and by most people.
And teachers answer them, without difficulties. For example:

*) Why do cars gain speed when moving downhill ?
Because of the net force. And we elaborate.

*) Why do we have day in New York when it is night in Tokio?
Because of the earth rotation. And we elaborate.

*) The shape of the moon changes from day to day; why is it so?... etc. etc.

Ludwik

http://csam.montclair.edu/~kowalski/life/intro.html

This question certainly resonated. I can usually shrug off this physics desire
for particle based descriptions of statistical, mass-population behavior,
taking comfort in the idea of 'emergent properties'.

But this time, I grappled with some pretend models myself.
Squeezing a tube of toothpaste: the paste is extruded faster than the squeeze moves,
no doubt. But is it at lower pressure?
Probably, but this reification is too remote to be helpful.
How about a two dimensional model?
Visualize an hour-glass cross-section model on a slight incline, so that marbles
tend to roll to the waist. If the hour glass board is placed on a shake-table,
do the balls translate faster in the waist? Probably.
But how to associate a lower particle speed with a higher particle translation rate?
I am reminded of the production warning that if spheres are handled in a cone,
they will jam, unless measures are taken.

Brian W