I suspect that BC was getting at the fact that even without "complicating
factors" such as air resistance and support flexibility, a simple pendulum is
isochronous only in the small-angle limit.
I think that the pendulum is taught in two contexts: (1) a historical one, in
which Galileo's observation was remarkable because he was paying attention to
the everyday world, and was able to turn the observation into a useful
scientific tool; and (2) we mention the isochronicity of pendula and then
immediately go on to show that, actually, real-world oscillators often are NOT
isochronous because of the following points.
Both contexts are excellent teaching points, and learning that a pendulum has
a constant period in (1) probably doesn't detract at all from learning the
intricacies in (2). I don't think that "unlearning" in this case is harmful at
all, nor does it take away from the impact of point (1).
/**************************************
As a species, we are forever sticking our fingers into the electric socket of
the Universe to see what'll happen next. It's a trait that'll either save us or
kill us, but by god it's what makes us human beings. I'd rather be in the
company of people who look at Mars than people who contemplate humanity's navel
-- other worlds are better than fluff. ~~Sir Terence David John Pratchett
***************************************/
________________________________
From: chuck britton <cvbritton@mac.com>
To: Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
Sent: Fri, September 10, 2010 7:43:53 AM
Subject: Re: [Phys-l] "Unlearning"
At 8:27 PM -0700 9/9/10, Bernard Cleyet wrote:
bc wonders if Ann teaches the pendulum is isochronous.
Bernie - you are a bit of an horologist so this is an example that
strikes home for you I suspect.
Was Galileo's observation/measurement that a pendulum is sorta
isochronous not one of his important contributions to science??
A purist knows that you need to consider the details of the support
mechanism, the thermal properties of the materials involved, the
viscosity of the air, the rotation of the earth and innumerable other
complicating factors.
But I'll maintain that it's good for young'uns to know that a
pendulum has a pretty constant period.
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