Re: Constraint and inertia

[Leigh Palmer <palmer@SFU.CA>]

> Some people say inertia instead of mass. Why do we need
> another term for mass? Inertia is not a physical quantity.
> Newton's first law is called the law of inertia, the law of
> tendency to preserve velocity.

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.

Leigh