Re: Name that force

[Bob Sciamanda <trebor@VELOCITY.NET>]

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.
-Bob Sciamanda

----- Original Message -----
From: "Ludwik Kowalski" <kowalskil@MAIL.MONTCLAIR.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, October 28, 2003 12:10 PM
Subject: Name that force


> In a conceptual question Hewitt asked what
> happens to the speed of an open freight car
> (increases, decreases or remains the same)
> when it rolls friction-free along a horizontal
> track while a pouring rain falls vertically.
>
> The expected answer is: "speed decreases
> as water accumulates in the car because the
> momentum must be conserved." What is a
> good name for a force responsible for the
> change in speed?
> Ludwik Kowalski