Re: momentum conservation in collisions

[Bob Sciamanda <trebor@VELOCITY.NET>]

John,

It may help to realize that

1) Force is the TIME rate of change of momentum; the duration of a force
in TIME alone is sufficient to cause a momentum change.

2) The "duration" of a force through SPACE is required to cause a kinetic
energy change; ie only if the affected particle moves through SPACE will
an acting external force affect its kinetic energy.

3) Since Newtonian force pairs are equal and opposite and necessarily have
the same time duration, momentum is conserved.

4) Particles interacting with equal and opposite forces can move through
different SPACE intervals and so can gain/lose different amounts of
kinetic energy.

Hope this is of some help.

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor


----- Original Message -----
From: "John Barrer" <forcejb@YAHOO.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Monday, March 13, 2000 4:42 PM
Subject: momentum conservation in collisions


> Pasted below is a message I have pestered others with
> recently. If it has already been posted here, I
> apologize for the redundancy.
>
> "How come energy can be dissipated (and usually is)
> during a collision but not momentum?" OR, "Why can
> energy either be dissipated within a system or to its
> surroundings, but momentum can ONLY be dissipated by
> leaking OUT of a system . . .