Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] F causes a



I have been quiet on this thread for a while (and probably should keep
quiet) but I continue to read it and continue to have thoughts and
questions about it. Here are a couple thoughts.

* * * Regarding the meaning of "cause" * * *

I am aware of the idea that a cause needs to precede the result. But I
have also been thinking about another common definition of cause that
was alluded to when Bob LaMontagne said that a ball bouncing off a wall
would have otherwise continued it's original path had the wall not been
there.

I think a lot of common people (ie not physicists) would accept that
"something" caused "something else" to happen if the "something else"
would not have happened if the "something" had not. It seems this
definition of cause allows "simultaneous cause-result" as well as
"delayed cause-result."

Just a thought!

* * * Regarding a block hitting you in the face * * *

Stefan Jeglinski asked if the force we feel when the block hits is not
caused by the acceleration of the block. I can imagine not saying the
acceleration is the cause. Rather I can imagine saying it was the
block's velocity relative to your face that caused the force that caused
the acceleration.

This is an extension of the idea that two different pieces of matter
cannot occupy the same space at the same time. Ignoring any nitpicking
about two atoms somewhat coexisting in space when their electrons mix to
form a covalent bond, and ignoring any nitpicking that might arise if I
personify the atoms of the block and your face... it seems that the
atoms of the block, because of their velocity relative to your face, are
trying to encroach upon the space currently owned by the atoms of your
face. This encroachment leads to a force as the atoms of your face
resist the encroachment. The ensuing force-pair accelerates your face
one way, and the block the other way.

The block's velocity caused the encroachment, the encroachment caused
the forces, the forces caused the accelerations.

Just another way of looking at it.


Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu