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At 07:42 AM 8/12/2006, you wrote:
----- Original Message -----
From: "Brian Whatcott" <betwys1@sbcglobal.net>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Friday, August 11, 2006 11:04 PM
Subject: Re: [Phys-l] Collision of irregular bodies
> 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.
Ok, I have to admit that I was visualizing a single point of contact.
Perhaps that was not what the op intended, but I thought that it was.
> 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.
Agreed. Now how about for a single point of contact? Can the mass
distribution, etc affect the direction of force as John D. implied?
Yes. Would you care for imaginary examples?