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Re: do not use calories



The calorie thread led to Dave's illuminating comments on the SI. The
benefits of SI were highly disputed from the very beginning. Gains do not
come without losses. Many of us witnessed the process of switching to SI.
As far as elementary teaching is concerned, what was lost and what was
gained? Did the gains justify losses?

But let me return to the sequencing issue ---> We should build on what
is below and not on what is above.

The logical sequence of topics in a typical introductory physics class
is the product of work of many generations of teachers. Perhaps the
"energy before force and work" approach will lead to a better sequence.
This may be a revolutionary change. But for the time being we have no
choice but to follow the evolutionary track, and to contribute to it when
we can. The long heat-energy thread illustrated frustration we experience
in dealing with the pedagogy of physics.

Let me repeat the original posting, in an abbreviated form.

Kilogram is now officially defined in terms of the mass of C-12. ....
Why bother to talk about ions, isotopes, atomic clocks and Avagodro
too early? This can only reinforce the feeling that "physics is not
comprehensible". What is gained [from explaining new definitions of
SI standards to those who are starting to learn physics]?

The same goes for using 4186 J/(kg*K) instead of 1 cal/(g*C), for water,
when we start teaching calorimetry. How can you explain Joule's paddle
experiment without calorimetry? How can you explain 4186 without a
reference to an experiment with which students are not yet familiar?
And how can you make them familiar with the experiment if they do not
know that the amount of internal energy, lost or received ("heat"),
can be measured.

My personal preference is to begin with calories and switch to joules
later. This approach protects me from explaining today's topics in
terms of what they will learn tomorrow. ....