Re: [Phys-L] force, momentum, torque, and angular momentum

[John Denker <jsd@av8n.com>]

Just so y'all know where I'm coming from:  The point of the exercise 
at
  http://www.av8n.com/physics/force-intro.htm
is to come up with definitions of force and torque (et cetera) that
are sufficiently clear and careful that they will never have to be 
unlearned.  If you think even one syllable of that document is not 
quite right -- except for brief passages marked as "roughly thinking" -- 
then please let me know.

On 07/23/2013 05:13 AM, Peter Schoch wrote:
> the idea of momentum "flowing" sounds a bit like "Caloric" flowing to
> me.  If we're trying to avoid saying heat "flows", then shouldn't we
> likewise avoid the idea that momentum "flows"?   While the concept of
> "flowing" makes it easier to teach now, when they get to more
> advanced levels it seems to me that they'll either have to "unlearn"
> the idea of "flowing" or amend it significantly to grasp more complex
> problems/concepts.

To me, conservation is synonymous with /conservative flow/ and 
I cannot imagine any other way of understanding what conservation
means.
 -- Energy flows.
 -- Electrical charge flows.
 -- Water flows ... in situations where we can pretend, to a 
  sufficient approximation, that each H2O molecule is 
  indestructible.
 -- Momentum flows.

I would not say that "heat" flows or "caloric" flows, but that's
because we don't have a sufficiently reliable definition of
"heat" or "caloric" ... not because there is any problem with
the definition of flow.

For details on what I mean by conservative flow, see
  http://www.av8n.com/physics/conservative-flow.htm

I've done enough fluid dynamics to have a pretty definite idea
of what "flow" means.  For example, if you want a careful,
non-sneaky derivation of Euler's equation, see
  http://www.av8n.com/physics/euler-flow.htm

If you think there are any "more complex problems/concepts"
that are inconsistent with my definition of flow, please
explain.  Examples would be particularly helpful.  Please be 
as specific as possible about the nature of the inconsistency.