Re: [Phys-l] Interactive Physics Simulations

[Ludwik Kowalski <kowalskil@mail.montclair.edu>]

My recollection is that one can turn an electric field (superimposed on 
the gravity field) at a specified moment of time. That should make your 
earlier approach workable, John, at least in principle. You wrote about 
assigning very large + and - charges to colliding objects. I would try 
to do this and turn the field on at the moment of zero-elasticity 
collision. (But last time I used IP was about 3 years ago. And my 
memory is not getting better.)

Ludwik Kowalski
Let the perfect not be the enemy of the good.

On Oct 9, 2006, at 3:45 PM, John Mallinckrodt wrote:

> On Oct 9, 2006, at 12:02 PM, Cindy Schwarz wrote:
>
> > you definitely CAN get things to "stick" in IP - I have done it in my
> > IP Workbook (which I also now have to boot into windows to run on my
> > macbook pro) - but rumor has it from the president of the company
> > that now has IP that they are indeed going to do an OSX version.
> >
> >
> > Anyway what you need to do is change the accuracy - (hence the speed)
> > - make the integration type different - time step smaller etc. cant
> > look at the program right now but its definitely "doable"
>
> Cindy,
>
> I suspect what you are thinking about is the case of a head on,
> totally inelastic collision in a gravity free environment.  In that
> very limited case, one doesn't need the objects to "stick" in order
> to remain (almost) in contact.  It is also true in this case that one
> needs to tweak the accuracy and integration methods to obtain a truly
> inelastic collision.  However, if the collision isn't precisely head
> on, then the angular momentum of the system will cause the two
> objects to separate and if, as in this case, one of the objects is
> suspended while the other is not, then gravity will cause them to
> separate.  Unless things have changed very recently, "sticking" is
> not, unfortunately (and somewhat mystifyingly), one of the options in
> IP.
>
> I'm pleased to hear that the publisher is going to do an OSX version,
> but trepid to hear the likely upgrade charge.