Re: [Phys-l] Interactive Physics Simulations

[John Mallinckrodt <ajm@csupomona.edu>]

Richard Bowman wrote:

> A totally (or completely) inelastic collision is one in which the
> colliding objects stick together after the collision

I disagree.  A totally inelastic collision is one in which the  
separation speed of the CM's of the colliding objects is zero JUST  
after the collision.  That doesn't guarantee, however, that it will  
remain zero.  If the system has angular momentum, the two objects  
will separate unless they ALSO stick together.

Having said that, allow me also to note that "collisions" are tricky  
beasts and it isn't always obvious when they "start" or when they  
"end."  In the case of collisions between objects that interact only  
via "contact forces" and that DON'T stick together, one can, perhaps,  
say that the collision ends at the instant the last contact ends.   
After all, as long as two non-sticking objects remain "in contact,"  
they will be exerting repulsive forces on each other.  A little  
thought may convince you that if the surfaces have ANY resilience  
whatsoever, then a truly inelastic collision is impossible UNLESS the  
two objects stick together.

John Mallinckrodt

Professor of Physics, Cal Poly Pomona
<http://www.csupomona.edu/~ajm>

and

Lead Guitarist, Out-Laws of Physics
<http://outlawsofphysics.com>