Re: [Phys-l] Collision of irregular bodies

[Brian Whatcott <betwys1@sbcglobal.net>]

At 06:19 PM 8/11/2006, you wrote:
> In the absence of tangential effects (friction or an equivalent) wouldn't
> any forces have to act perpendicularly to the surfaces at the point of
> contact?  I'm assuming that this is what is intended by the term "action
> reaction pair".  I suppose this would be problematic if one "surface"
> consisted of an infinitely sharp point, but otherwise I'm not sure how the
> force directions can be different?

Two irregular smooth bodies can meet at a point or several points,
 a line or several lines,  a surface patch or several surface patches
or any combination of these.
If this third case comprised an object with an extrusive conical surface,
 and another object with an intrusive matching, coaxial conical surface,
 though exceptionally unlikely in the physics model universe, this union
would initially act like a high friction contact, no matter if the surfaces
 were friction -free except if one rotated wrt the other on that axis.



Brian Whatcott    Altus OK    Eureka!