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Re: [Phys-l] Centrifugal redux

Thanks, Joe. You said it much better than I would have. My response was "so let's just tell them Newton's 1st law isn't that important." Of course, we ALL have to apologize to the general relativists because we keep talking about those fictional gravitational forces instead of exposing them to the complex beauty of space-time curvature and its effect on basketballs. :)

Bill

Joseph Bellina <jbellina@saintmarys.edu> 3/18/2009 11:59 am >>>
It seems to me that if you accept the student's answer you have just
lost a marvelous opportunity to reinforce the deeply counterintuitive
notion that constant velocity not at rest is the natural state of
things. Why would you waste such a gem of an opportunity to revisit
an important idea in a new framework...a key strategy in supporting
conceptual change.

cheers,

joe

Joseph J. Bellina, Jr. Ph.D.
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556

On Mar 18, 2009, at 12:53 PM, Philip Keller wrote:

I agree. If a student says that a satellite remains in orbit
because the gravitational force balances the centripetal force, I
can't say "No, you are wrong." If I insist on banishing
centrifugal forces from my class, the more honest response is: "No,
I don't want you to think about it that way." Maybe better to open
the door...time spent explaining why these forces do not really
exist could just as easily be spent explaining when it's OK to use
them.

***********

So what is the point of forcing students to go through an intermediate
phase where they are taught centrifugal fields don't exist? For all
of their life before class, after class, and north/south/east/west of
class, centrifugal fields exist.

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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l