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Re: [Phys-l] Equations (causal relationship)



Thanks, Ken, for both advices.
Jack


On Wed, 3 May 2006, Ken Caviness wrote:

I wasn't going to make a fuss about the typos, but as long as you're making corrections, the quote should be:

Après moi le déluge.

In case some here can't see the accents, that's a grave accent on the "e" in "apres", an acute accent on the first "e" in "deluge". Interesting that even the Merriam-Webster OnLine site incorrectly omits the latter -- as do many others, I just googled the phrase.

Nice quote, by the way. Certainly applicable here! Don't tell anyone that you're Louis XV, though, they'd lock you up. ;-)

Ken Caviness
Physics, Southern Adventist University


-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Jack Uretsky
Sent: Tuesday, May 02, 2006 10:39 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Equations (causal relationship)

Good heavens! Brain disegaged. Sorry.
Apres moi les deluge.
Jack


On Tue, 2 May 2006, Jack Uretsky wrote:

Hi all-
Inarticulately, I guess, I tried to make the point that in
F=ma it is totally arbitrary as to which of the three variables is called
a "caues", and which, if any, is called an "effect".
Apre' ma, les deluge.
Furthermore, the "deluge" demonstrates that the choice is strictly a
matter of taste and your faith in your understanding of the learning
process.
I guess it is therefore accurate to say that the discussion
is about faith-based teaching.
Regards,
Jack




On Tue, 2 May 2006, Rick Tarara wrote:

To move along the lines that John Clement has opened, a prime reason for
dealing with Forces as the cause of accelerations is in terms of the
(mis)conceptions/instincts with which the vast majority of students come
into physics. Straight from Aristotle they believe that all motion requires
a sustaining force along the direction of motion. Far too many will STILL
believe this upon leaving our courses.

That forces _cause_ accelerations then is a pretty important concept--forget
all the wrangling about commutivity, etc. That motion (velocity) does not
necessarily involve forces but rather changes in the motion (velocity) do,
is a difficult concept that can take considerable time and effort get
across. Using the equation a=net_F/m and the concept that the acceleration
of an object is caused by the vector sum of the forces acting on that object
seems to me to be all but essential to such instruction.

Of course, we shoot ourselves in the foot because of the wide-spread and
historical tendency to write F = ma (in all it's algebraic forms) instead
of net_F = ma (which we all of course understand, but which students
certainly do not). The algebraic logic some have been using to argue the
points of this thread are more valid with the latter form than with the
former, but for the novice (and perhaps terminal) physics student, the
concept of causation of accelerations due to forces is (as JC has reported)
a useful path towards a better Newtonian understanding of nature.

Rick

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Saint Mary's College
Notre Dame, Indiana
rtarara@saintmarys.edu
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