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Hi --
I have noticed some introductory physics books like to introduce
the concept of /inertia/ ... and then define mass in terms of inertia.
In contrast, there are plenty of highly respected physics books
that define mass directly, without mentioning inertia.
Maybe I'm missing something, but I have to ask: Why would anybody
bother introducing the concept of inertia? Why not cut to the chase?
Why not take whatever process is being used to define inertia and
use it to define mass directly?
From a tactical and pedagogical point of view, it seems like a waste
of effort to define two concepts when only one is needed.
From a technical point of view, I'm not even convinced that the
vernacular notion of "inertia" corresponds all that closely to
mass; I suspect many students (and many adults), if they thought
about it at all, would say that a fast-moving car has "more inertia"
than a slow-moving car, as manifested by the fact that it is harder
to steer it around a sharp corner.
So this brings us back to the pedagogical principle that learning
proceeds from the known to the unknown: You can't define mass in
terms of inertia unless the students already have a reliable notion
of what inertia is ... which they almost certainly don't. They might
have no idea, or they might have wrong ideas.
I leave it as a question: Is there any scenario in which it makes
sense to introduce the concept of "inertia" in the introductory class?
========================
If this comes down to another case of "we have to cover it because
it's in the state-mandated standards" I'm going to tear my hair out.
I quote from http://www.p12.nysed.gov/ciai/mst/pub/mststa4.pdf
• explain and predict different patterns of motion of
objects (e.g., linear and angular motion, velocity and
acceleration, momentum and inertia).
No mention of mass ... just inertia. Aaaarrrrrgggghhhh!!!!!
These asinine standards and tests defeat the purpose of having an
educational system. This has got to stop.
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