Re: [Phys-l] nifty pendulum, conservation, et cetera

[John Denker <jsd@av8n.com>]

Carl Mungan wrote:

> > http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/mechanics/mech1m/galileop.html
>
>
> I strongly prefer using this apparatus to do the standard demo of how 
> high a particle must be released to just complete a loop-the-loop. 

Yes indeed.

There's another way of approaching this, which is also amusing.
Make it a theoretical physics exercise to predict the X,Y position
of the highest point of the swing, for a given post position, as
a function of the height of release.

It's an easy question, requiring little more than conservation,
high-school geometry and some common sense ... but often students
forget to apply common sense.

The trick is that the solution has two branches, and having
found one branch, non-experts are hypnotized by it, and can't
or won't go looking for the other branch, even though it is
trivially findable.

=================

It's also amusing to do the error analysis on this critter, i.e.
to understand why it works so well.