Re: Inertia or the "amount of substance"

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

My comments were about the way of introducing a concept,
not about ways of refining it in subsequent courses. You are
correct, Miguel, initially introduced concepts must be refined,
as needed. Teaching would be impossible without this. A
misconception, I think, exists when a statement is nearly
always wrong, not when situations in which it is wrong are
uncommon.

A discussion on how to introduce "getting fatter and fatter",
when v-->c, would be interesting. Is it an illusion or is it real?
And what happens to the mass? Is this the area in which a
distinction between the "two masses" becomes essential?
Ludwik Kowalski
********************************************************
To understand is to find a satisfactory causal  relation.
To explain is to express that understanding.
To teach is to promote understanding.
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"Miguel A. Santos" wrote:

> ... I'd say that the conception of mass "as the amount of
> substance which can not be changed without taken somehting
> away, or adding" may be a misconception*. Namely, as I move
> faster and faster, relative to someone else, I see her/him getting
> fatter and fatter, and she/he is not eating that much. It is the
> inertia which is increasing. .....