Re: [Phys-l] Collision of irregular bodies

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

In thinking about and reading the posts, Brian, it seems to me as if there 
is a disconnect in how people are interpreting the original question (as a 
matter of fact, did we actually lose the original poster right after his/her 
question?).  The original poster referred to the "action reaction pair", 
which to me, and apparently to Chuck, means the forces on the two objects 
when they collide.  However, it seems as if some posters are considering the 
EFFECT that the collision would have on the colliding objects rather than 
the force between them.  In the example below, you rightly noted that the 
effect of this collision on the RED ball will be different than the effect 
on the BLUE ball...  However, in either case, barring fricitonal or other 
tangential forces, the FORCE on either object will be normal to the surfaces 
at the point of contact, yes?

----- Original Message ----- 
From: "Brian Whatcott" <betwys1@sbcglobal.net>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Cc: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Sunday, August 13, 2006 10:17 AM
Subject: Re: [Phys-l] Collision of irregular bodies


> At 05:15 PM 8/12/2006, Chuck Britton wrote:
>
> > ///
> > My imagination is looking forward to examples where the mass
> > distribution WILL affect the direction of the contact force.
>
> ///
>
> > > >  > Can the mass distribution, etc affect the direction of force?
> > >
> > > Yes. Would you care for imaginary examples?
> >
> >
> >         eagerly anticipating examples.
>
>
> Continuing with the dumb bell example, I offer this:
>
> consider a sphere of diameter 3 distance units, and mass of 27 mass units
>  moving in deep space at a speed of 1 speed unit.
> It makes a direct hit on one of two spheres comprising a dumb bell
> whose mass in total is 1 mass unit, 99.9% of which is situated in the
> red dumb bell sphere,  held by a connecting rod at 100 distance
> units from the blue dumb bell sphere.
>  In my frame, the dumb bell was stationary and its rod was in a
>  line normal to the trajectory of the impacting sphere.
> Consider the effect of the impact if it is the Red sphere which is hit
> alternatively if the Blue sphere is hit on a radial line normal to
> its connecting rod.
>
> .
>
> .
>
> .
>
> .
> Oh yes:  in space, oxide films do not build, so impacting surfaces weld.
> :-)
>
>
> Brian Whatcott    Altus OK    Eureka!