Re: Newton's 3rd law? was Re: inertial forces (definition)

[brian whatcott <inet@INTELLISYS.NET>]

At 15:59 10/25/99 -0500, you wrote:
> Leigh Palmer wrote:
>
> > ... I have never used what
> > should be the standard terms for curvilinear motion: tangential,
> > normal and binormal components of acceleration and force. I note
> > that the binormal components of these quantities are always zero.
>
> Leigh
>
> I had to look up binormal in my Funk & Wagnalls. The definition sounds
> like that for normal. What's the difference?
>
> poj

This definition sounds marginally clearer:

"Principal normal to a space curve at a point.
 The line perpendicular to the space curve C at the point P
of C and lying in the osculating plane of C at P.
 The positive direction of the principal normal to C at P
is chosen so that the tangent, principal normal, and binormal
to C at P have the same mutual orientation as the positive
x, y, and z axes."

You can see this is consistent with:
"Binormal - binormal to a space curve at a point.
  The line passing through the point, and normal to the
osculating plane of the curve at the point...."

 Point P is called a tacnode.
An example of which is the origin of the curve y^2 = x^4(1-x^2)
 The double tangent there is the x axis

    (it says here....Math Dictionary, James&James, D.Van Nostrand.)



brian whatcott <inet@intellisys.net>
Altus OK