Re: "Simple pendulum"

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

JACK L. URETSKY referring to:

> > It is not true that a conical pendulum can be viewed as
> > a superposition of two "mutually perpendicular" simple
> > pendula oscillating with the same frequency and same
> > maximum spherical angle TET. Why not?

wrote:

>         I  don't understand the question.  Why on earth
> should they be?  It's like asking why isn't a marching
> band like a french fried potato (somebody think up a
> punch line to go with this question).

Every misconception can be ridiculed by those who
know better. But it REALLY WAS my misconception.
Where did it come from? Probably from knowing
that, mathematically, a circular motion with constant
speed is a superposition of harmonic oscillations along
the x and y axes. The equality of amplitudes and the
phase difference of 90 or 270 degrees always leads to
circular motion.

Are you opposing the idea of collecting misconceptions,
Jack? I mean misconceptions some of us had, and also
those we identify in minds of students. No, I am not
referring to misconceptions such as "cows must drink
a white fluid to produce white milk."

Jack also commented on the idea that

> > the concept of perpendicularity does not apply
> > to curved lines.

He wrote:

> Say what?  Lines of latitude and lines of longitude
> on a sphere are curved and respectively perpendicular
> to each other.

Only very short segments near the intersection points
are nearly perpendicular. In my terms if a line A is
perpendicular to a line B then any segment of A must
be perpendicular to any segment of B (in old geometry).
I would say that "planes of latitude" and "meridian planes"
are perpendicular, but the lines you are referring to are not.
What is wrong with this position?
Ludwik Kowalski