Re: [Phys-l] "unlearning"

["John Clement" <clement@hal-pc.org>]

> Used his pulse while sitting in church watching a candelabra swing
> after being set in motion when initially lit.
> Noted that the period remained 'the same' as the amplitude decreased.
>
> SO - was his pulse speeding up or slowing down as the service progressed.
> 	(Question for questioning students)
>
> another question might be to to estimate how large an angle might be
> expected for such a pendulous candelabra.
> 	(I would expect it to be WELL in the range of 'small angles'.
> 		But my days of such lighting are well behind me)
Actually is very small for small angles.  One way of demonstrating this is
to take 2 identical pendula side by side and start them both with different
amplitudes.  For a decent number of swings they stay in phase quite well.
Some teachers have students compare a 90 degree angle with a small one, but
they only count the number of swings for a short time.  I wonder if any
groups notice the difference in period.  This is actually in one of the
standard 9th grade lab books.  Yeuch.  Does the teacher even know that the
students might come up with the correct answer that in this case the periods
are easily found to be different?

John M. Clement
Houston, TX