Re: Inertia

[brian whatcott <inet@intellisys.net>]

At 10:50 11/28/97 -0800, you wrote:
> > It should be noted that in the older literature, the word translated as
> > "Force" isn't necessarily force in the modern sense. It often meant
> > "property of" or "capacity for" or "tendency to". So we shouldn't confuse
> > Newton's "Force of inertia" with the F (or -F) in F=ma.
> [Donald S]
....
> Rather than distinguish two kinds of forces we now call them both simply
> "force". *Vis inertiae" is a force of the latter kind, a force inherent
> in an object, measured by its coefficient of inertia, which appears
> whenever the object is subjected to a net external force.
> ...
> Leigh
I am possibly being obtuse, but the eight definitions provided by 
Newton are not abstruse. He says:
"...I have laid down the definitions of such words as are less
known, and explained the sense in which I would have them to be
 understood in the following discourse..."

His definitions go like this:
I
Quantity of matter is conjunction of density and bulk
[as condensed by compression or liquefaction - with no
regard to interstitial space...]
 this looks reasonably like 'mass'.

II
Quantity of motion is conjunction of velocity and
quantity of matter.
 this looks reasonably like 'momentum'.

III
Inertial Force
 A body only exerts this force when another force
impressed on it attempts to change its condition.
 this looks reasonably like reaction force.

IV
An impressed force is an action exerted upon a body,
in order to change its state, either of rest, or of 
uniform motion in a right line.
 this looks reasonably like external force.

V, VI, VII, and VIII
All deal with definitions concerning centripetal force.

Sincerely


brian whatcott <inet@intellisys.net>
Altus OK