Re: Inertia

[Leigh Palmer <palmer@sfu.ca>]

Durig Lewis makes an important point:

> I have a couuple of questions:
>
> How do we define force?
> How do we define mass?
>
> I have often heard physicists define each using Newton's second law, not
> realizing their circular argument.

I think one should spend some considerable time at the outset in
an introductory physics course helping the student to recognize
this important fact. The argument my teacher made when I first
encountered this dilemma was that one of these quantities must
remain undefinable. In fact he introduced us to the old standards
of mass, length, and time as standards of "three fundamental
undefinable quantities".

I think we become so used to not needing definitions when using
these quantities that we lose sight of their ambiguous status.

Leigh