Re: centrifugal force (cont)

["John S. Denker" <jsd@MONMOUTH.COM>]

Bob S. wrote:

> We have done
> the "un-muddying" for the rotating observer only because it is do-able
> (that's all we ever study in texts/classes)

That doesn't say anything special about rotating
observers.  Some people say almost all of physics
is "the art of the possible".  Some people say
almost all of pedagogy is "the art of the possible".
If this is a criticism, it is about the mildest
criticism I can imagine.

>There is otherwise no fundamental reason for singling out the
>centrifugal/coriolis effects from among the infinite possibilities of
>"observer-accelerated " effects.

RAUBER, JOEL wrote:

> There may not be a fundamental reason, but there are some very practical
> reasons for singling out those effects.  For starters, we live in such
> reference frames.  We often travel in vehicles that constitute such
> frames.
>
> Furthermore, to the extent that general motion of a rigid body can be
> broken
> into to translation plus rotation than such effects really are
> fundamental.

Yes!

Since the second law is a second-order differential
equation, and since differentiation is a linear
operator, and since the change of reference frame
is a linear transformation, if we learn to deal
with ordinary straight-line acceleration (gravity-like,
acceleration in same direction as velocity) and
also learn to deal with cross-wise acceleration
(centrifuge-like including Coriolis) together those
are, AFAICT, a complete package.  To second order,
that's all there is.  And second order is all you
need (at a single point anyway;  analyzing extended
regions require the full GR machinery in general).