Re: Inertia and Lenz's Law

[Leigh Palmer <palmer@sfu.ca>]

>    I was at a talk where a physicist stated that pulling a table cloth out
> from beneath a set table was not truly a demonstration of the property of
> inertia.  What is your sense of this?

I'd say that it is a pretty direct demonstration of inertia - or else
the absent-mindedness of the professor who uses a tablecloth with a hem.

>    Also, he said the demonstration where an aluminum ring is placed on an
> iron core stand that is surrounded by a transformer coil does not truly
> demonstrate Lenz's Law.  What is your sense on this one, too.

It's one of the very best demonstrations of Lenz's law I can think of.

>    Are these demos, like the explanation that a skater melt the ice in
> order to skate, part of the folklore o'physics?
>
>    If anyone has a great inertia demo they wish to share, I would like to
> hear about it.  I have one that astounds students.  I get flat poker chips,
> and stack them in alternating colors (using school colors, of course).  With
> a steel rule that has a thickness that is less than a chip, I rapidly wave
> it back and forth, each time knocking out the bottom chip.  It sorts them
> and astonishes the students.  But, like the tablecloth, is this not really a
> demo of the Property of Inertia?

You don't do that one with standard interlocking poker chips, do you?
They are the ones that are almost automatic to stack. I've only rarely
seen any other kind outside a casino, though when I was a kid we used
flat, smooth cardboard chips.

Leigh