Re: Banked road

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

"D.V.N.Sarma" wrote:

> It is the interpretation of the observer that an outward force is acting
> on him when he is in a rotating frame. What he actually feels is the
> pressure between him and sides of the car. Since he knows that
> he is not exerting any muscular effort to produce this pressure and
> since he cannot bring himself to believe that an inanimate thing like
> a car can exert such a pressure on him, he interprets that some
> mysterious force is pushing him towards the sides of the car. This
> he calls 'centrifugal force'.

I wouldn't have said that.

It is not traditional and not recommended to ask what the observer "feels".
Observers are paid to observe the objects in their vicinity, not to worry
about what they themselves are feeling.

The centrifugal field is profoundly analogous to the gravitational field.  It
depends on the reference frame, not on the observer _per se_.  If I observe an
apple falling under the influence of gravity (or centrifugity) I don't need to
be attached to the apple to know that it is accelerating relative to the
chosen frame.  And I don't really need to be attached to the frame;  I just
need to measure things relative to that frame.  I don't need to feel the apple
or anything else.  The apple's acceleration is not determined by perception of
muscular effort or anything like that;  the acceleration can be observed
directly.

Bob Sciamanda wrote:

> I think it needs this over-emphasis:  In the Newtonian scheme the
> centrifugal and coriolis effects are not the result of any non-inertial
> properties in the (absolute) motion of the observed object - they are
> completely the result of the non-inertial properties of the observer's
> motion.  They are not observed by an inertial observer - they "taint" ALL
> the observations of the rotating observer.

I 100% agree in spirit, although I would have said "frame" rather than
"observer".