What is Inertia

[Richard Brekne]

"Don A. Gilmore" wrote:
>>  1. Don Gilmore... inertia is a concept, not a quantity, has nothing to
>> do with size, mass, velocity or anything else. Is simply the fact that
>> objects with mass tend to resist any change in velocity. No object
>> regardless of mass has any more inertia then any other mass.
>>
>> 2. Sarah and Mark.... inertia is very much like Don describes, yet
>> inertia is mass related... a larger mass will definatly have more
>> inertia then a smaller mass.

>This is about as close as we're going to get here.  I'm not going to
>nitpick.

Is it nitpicking then when one says inertia is not a quantity, and
another states that it is more or less porportional to mass ?? Please
explain why this difference is of no consequence.

> 
> When Jim says "mass x velocity-squared" he is probably referring to kinetic
> energy (which is actually 1/2 that much), which would be in energy units of
> joules, or foot-pounds.  The reference to acceleration-squared is probably
> just a typo.  Acceleration squared doesn't apply to anything in physics.
> 
> > "Inertia is a minifestation, a property, an effect, of acceleration and
> > deceleration.  It's proportional to the square of the change in speed,
> > or velocity."
> 
> I'm not sure who that quote came from but  it's *way* out there.  This is
> nonsense pulled out of the air.

That came from Jims last post. 
> 
> > What I'd like to see at this point is that since Don, Sarah, Mark, and
> > Jim all are people we all rely on for physics insights, and because they
> > all present clearly different definitions of this concept,,, that these
> > four all bang this one through until they arrive at a common definiton
> > for us.
> 
> I think we're pretty much there. 

Well, you have me on board anyways.. but at least a posts came in
echoing the <<inertia is associated with velocity>> line from interested
readers. And I dont think you have Jim quite onboard either... or
perhaps I misinterprete his use of language.

It just strikes me as relatively important to have the same working
definitions of this (and other) concepts in discussion... to avoid
talking right past each other for one thing.

Cheers
RicB