Re: Constraint and inertia

[Paul Middents <pmiddents@KENDACO.TELEBYTE.COM>]

I think Newton was aware of the two attributes of mass. Prop. 24 of Book 2
in the Principia describes pendulum performance. He ends the proposition by
saying "And by experiments made with the greatest accuracy, I have always
found the quantity of matter to be proportional to their weight." Newton, in
his wisdom commented no further on this remarkable fact.

As an aside, I was led to this passage by a very valuable book which I just
became aware of: "The Newton Handbook" by Derek Gjertsen., (Routledge and
Keegan Paul) 1986.

Paul Middents
Olympic College
Bremerton, WA

Leigh Palmer wrote:

> Mass is the coefficient of inertia. It expresses the strength
> of the tendency to "preserve velocity" quantitatively. "Mass"
> has another function, its gravitational effect. Thus "inertia"
> refers only to one attribute of mass. The terms are not
> interchangeable in all contexts.
Ludwig wrote:

Was Newton aware that a "material object" has two attributes:
inertia, which appears in F=m*a, and mass, which appears in
the law of universal gravitation? Probably not. Who was the
first to make a clear distinction, and to show experimentally
that under common conditions the two physical quantities
(attributes) are identical?

In teaching we take the identity of mass and inertia for granted
when the mass of our planet is deduced from Cavendish data,
and from the value of g.