Re: Banked road

[Vern Lindberg <vwlsps@RITVAX.ISC.RIT.EDU>]

> "Ludwik Kowalski" wrote:
>
> I think it is not only a matter of language; suggest another
> name and I will probably have no objection (unless the word
> is already used to describe something else).
>
> Let us refer to a cylindrical pipe whose inner surface is used
> as a road for a car of mass m traveling along a circle r with a
> constant speed, v. Suppose the cylinder is located far away from
> all stars and that its mass is M. I am at rest in a frame of
> reference which Newton would call "the frame of fixed stars."
>
> To simplify assume tham M>>m so that the pipe is at rest in
> my frame of reference. I see only one force acting of the
car; it is the CENTRIPETAL force toward the center Fc=m*v^2/r.
> It is the normal force, N, with which the pipe acts on the car.

I would not use "centripetal force" to refer to forces in an inertial
frame, since "centripetal" is just the direction.
It is the Normal force, plain and simple. Almost no one takes Latin
any more, so I would not even use "centripetal" when "radial,
inwards" is plainer language these days.

> The car acts on the pipe and the pipe reacts with an equal and
> opposite force. If the reaction is real (not fictitious) then
> the action is also real in my frame of reference. We need a
> name for the force with which the car acts on the cylinder.
> What is wrong with CENTRIFUGAL?

The force already has a correct name, **Normal**. "Centrifugal" is
just its direction, and I would prefer "radial outwards.
--
Dr. Vern Lindberg   New Area Code Nov 15 585-   716-475-2546
Department of Physics           Fax 475-5766
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