Re: [Phys-l] [PTSOS] perfectly inelastic collision- velcro vs magnets?

[Bernard Cleyet <bernardcleyet@redshift.com>]

I think this is an excellent "problem".

I only add to the separation for the increase in energy (later transferred to KE and then dissipated) as the creation of the magnetism itself.

bc wonders what say (write) others.

p.s.  Better data?  Yes a comparison might be instructive.


On 2011, Oct 27, , at 10:10, Dan Burns wrote:

> I think using the magnets might cause some confusion, I use velcro. The energy added by the magnets came from whomever separated them.  This increases the kinetic energy of the system but not the momentum. As you note, it is an internal force. Each glider does have more momentum but one has negative, the other positive.
>
> I think doing the magnet experiment is a great idea if you contrast it to using velcro and discuss the differences.

and lack thereof.

> Dan
>
> On 10/26/11 9:54 PM, "tarshis.darren" <tarshis.darren@gmail.com> wrote:
> >    
> > One of the labs I do for momentum is to show that momentum is conserved for a variety of collisions between two gliders on an air track. A question has been bothering me for the last couple years: When I demonstrate the perfectly inelastic (sticky) collision, I have been using a magnet attached to each glider to get them to stick together. I don't believe this magnetic force affects the total momentum because: 1) it is an internal force in the system, and 2) Newton's 3rd law says that the force right on glider A is equal and opposite to the force left on the second glider B. 
> >
> > My concern is with the energy. As the two gliders come together, doesn't magnetic potential energy convert to kinetic energy? Does this affect the total momentum? Am I safe to use magnets to demo this, or should I switch to velcro for better data?
> >
> > D. Tarshis
> > Leadership Public Schools - Hayward