Inertia and Physics.. Paul Chick

[Don A. Gilmore]

----- Original Message ----- 
From: "Sarah Fox" <sarah@gendernet.org>
To: "Pianotech" <pianotech@ptg.org>
Sent: Friday, December 26, 2003 10:07 AM
Subject: Re: Inertia and Physics.. Paul Chick


> LOL!!!  No, not *that* sort of Ph.D.!  Remember, I'm a neurobiologist!  I
> had a year of physics in high school and a year in college -- and did
> wonderfully in both courses -- and even remembered a bit of it into middle
> age.  However, Don knows gobs more about mechanics than I ever will.
>
> I think we're quibbling over semantics here, though.  For the sake of
moving
> forth with our understanding of this problem, technicalities aside, I
think
> we can regard "inertia" as "mass" in a translational sense and "rotational
> inertia" as "rotational mass" in an angular sense.  (Don and I both,
> independently, have used the latter term, BTW.)
>
> Right, Don???
>
> Peace,
> Sarah

Right Sarah.  We have 99% of this ironed out (and 100% of anything that
really matters!).

The inertia that an object exhibits depends on how much mass it has.  One is
not "proportional" to the other because proportionality could be stated
mathematically with an equation, like

inertia = X * mass

and would have units.

And "inertia" is not really synonymous with "mass" because it wouldn't be
proper to say, "I have an inertia of 80 kg", when you should use the word
"mass".

A correct sentence would be, "Because of the effects of inertia, it takes
one newton to accelerate an object with a mass of 1 kilogram at one meter
per second per second."

Don A. Gilmore
Mechanical Engineer
Kansas City