Re: Name that force

[Bob Sciamanda <trebor@VELOCITY.NET>]

Yes, momentum is always conserved.  My point is that if the interaction
between two bodies (with different initial velocities) is to produce a
common final velocity, conservation of momentum mandates that the
interaction mechanism include a dissipation of kinetic energy.  Without such
a dissipative mechanism, momentum will be conserved, but a common final
velocity will not be  achieved.
-Bob Sciamanda

----- Original Message -----
From: "John S. Denker" <jsd@AV8N.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, October 28, 2003 12:12 PM
Subject: Re: Name that force


> On 10/28/2003 10:12 AM, Bob Sciamanda wrote:
> > These are  totally inelastic collisions (interactions) between the
> > car and the water.  Ie., interactions between two objects resulting
> > in a common final velocity.  This can only happen if the interaction
> > includes a dissipative mechanism.  Conservation of momentum mandates
> > the dissipation of kinetic energy.
>
> That is a good approximation and correctly (for all
> practical purpose) describes *what* happens, but the
> result holds more generally -- momentum is conserved
> even if there is no common velocity;  momentum is
> conserved even if there is negligible dissipation.