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Re: [Phys-L] inertia and the tablecloth demo



Hate to be pedantic or repetitive - but while certainly zero kg-m/s is a
legitimate momentum, it is only so for particular reference frames...

On Fri, Aug 19, 2016 at 7:40 AM, Richard Tarara <rtarara@saintmarys.edu>
wrote:

I think that all of Newton's Laws can be expressed in terms of momentum.
Isn't that essentially what Newton did? While we separate them into three
distinct 'laws' it seems to me that they are all aspects of the same basic
physical phenomena.

I would also consider zero to be a legitimate momenta (consider recoil
situations).

rwt



On 8/18/2016 10:55 PM, Anthony Lapinski wrote:

I would not equate the first law with conservation of momentum. If an
object is at rest, it has no momentum but still has mass (intertia).

On Thu, Aug 18, 2016 at 10:40 PM, Richard Tarara <rtarara@saintmarys.edu>
wrote:

Except that Newton's First Law is often referred to as the Law of
Inertia. I think most here would say that the first law is about
momentum
and the conservation of such in the absence of external net forces. I
used
to have an animation that I used in class showing how an astronaut in
space
could be crushed between two 'weightless' elephants. In reality they
worried about getting crushed between the shuttle and Hubble. So, at
least
in my mind, inertia has been used not just for mass but for something
moving that is difficult to accelerate (usually to stop or deflect).
Yes,
the main focus is on the mass, but not exclusively so, or so it seems to
me.

rwt

On 8/18/2016 7:35 PM, Jeffrey Schnick wrote:

I consider mass and inertia to be the same thing. Inertia is the word
one tends to use when one is talking about the concept and mass is the
word
one tends to use when one wants to assign a value to it. It is often
said
that "Mass is a measure of inertia." (That phrase, in quotes, gets
65,100
hits on Google.) I prefer "Mass is inertia." which only gets 18,200
hits.



--
Richard Tarara
Professor Emeritus
Saint Mary's College

free Physics educational software
http://sites.saintmarys.edu/~rtarara/software.html

_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l



--
Richard Tarara
Professor Emeritus
Saint Mary's College

free Physics educational software
http://sites.saintmarys.edu/~rtarara/software.html

_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l




--
Todd K. Pedlar
Associate Professor of Physics
Luther College, Decorah, IA
pedlto01@luther.edu