[Phys-L] Re: Momentum Again

[Brian Whatcott <betwys1@SBCGLOBAL.NET>]

At 10:16 AM 12/7/2005, Rick, you wrote:
> I still think most people are missing the reason for the question about
> exactly 1/2 of the KE being transferred in a perfectly inelastic collision
> between same mass objects, one at rest.
>
> The question, as I read it, is HOW is exactly 1/2 transferred?  Restating
> the math of momentum conservation or stating that no real-life situation
> actually behaves this way, is not, if I interpret the question properly, an
> answer.  Here is what I imagine a student thinking:
>
> "A ball is moving along at speed v, has momentum mv, and KE .5mv^2.  Now
> there is this collision, and after the collision, the math says that only
> half of the energy is KE.  But where did the rest of the energy go?  Heat,
> sound, deformation--OK, but HOW does exactly 1/2 of the original energy find
> its way into these other channels, none of which are very well defined nor
> necessarily exactly the same from collision to collision."

///

> Rick

I suggest this is a better response to a question like this:

There is a range of possibilities in losing energy during a collision.
The spectrum ranges from essentially non to as much as one half the
  kinetic energy.
We know the upper bound is fixed and it occurs if both objects travel on
at the same velocity.   The interval during which this loss process occurs
  depends on the available  means of dissipating the energy.
  If only low loss means are available - the dissipation takes some
extended period  and/or displacement and is often oscillatory.
If high loss means are available, the process is fast.



Brian Whatcott    Altus OK    Eureka!
_______________________________________________
Phys-L mailing list
Phys-L@electron.physics.buffalo.edu
https://www.physics.buffalo.edu/mailman/listinfo/phys-l