Re: [Phys-l] Collision of irregular bodies

["R. McDermott" <rmcder@gmail.com>]

----- Original Message ----- 
From: "Ludwik Kowalski" <kowalskil@mail.montclair.edu>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Saturday, August 12, 2006 9:13 AM
Subject: Re: [Phys-l] Collision of irregular bodies


> On Aug 12, 2006, at 8:42 AM, R. McDermott wrote:
>
> > . . . Now how about for a single point of contact?  Can the mass
> > distribution, etc affect the direction of force as John D. implied?
>
> I think that the mass distribution would affect the consequence of a
> collision but not the direction of the pair of action-reaction forces
> at time zero. I am thinking about the duration of collisions. During a
> collision the direction of the line along our pair of forces is
> probably changing. So what is true at the moment at which forces start
> to act (t=0) does not have to be true when deformations develop. Is the
> collision in question elastic or is it inelastic?

Heh, it's kind of funny how every discussion encompasses increasingly 
complex possibilities as it develops.  Well, I was thinking about the 
hypothetical non-deforming, elastic, simplest case.  I can see where 
deformation could result in changes in direction of the action-reaction pair 
as time goes on.  Again, considering an ideal case of one point of contact, 
and no possibility of tangential forces at that point, even though the 
direction changes with deformation can we ever have forces that are not 
normal to the surfaces?