Re: definition of energy (without work?)

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

Joel Rauber wrote:

> This "ecclesiastical court" declares Feynman innocent of introducing
> work before conservation of energy; as ably defended by council
> Denker; but notes with a raised eyebrow that he did use the word
> "work" in chapter 4; and we're going to have to keep an eye on that Richard
> guy.  :-)

I did open Chapter 4 of Feynman and I reread the first two sections.
It is a great description for those who already know physics. But I
have enough experience to predict that the approach would be a
disaster if used in a class for novices, either in a high school or a
college. The author clearly recognizes this; see the footnote which
refers to the efficiency of Carnot's steam engine on p 4-2. Or
see the next page where it is written  "in high school we learned
a lot of laws about pulleys and levers."

Let me pretend to be a novice. First the teacher shows me a
seesaw. S/he gives me "units of weight" and asks me to do an
experiment. OK, I can balance the weights as shown. But what
does s/he mean by saying it is "a self-contained machine". This
seesaw is not a machine and it is not self-contained. I must
manipulate it. And what is this business of "reversible and
not reversible self-contained machines"? I see many sentences
which make no sense to me.

Then s/he showed me another machine (Figure 4-2). I am a
concrete operational creature and I am not able to figure out how
this gismo works. Why does s/he wants me to answer this question
"without looking at the interior mechanism" (page 4-3). This is
impossible at my level. And I am again confused by the word "self-
contained"; somebody must push the balls horizontally. The word
"load" and "unload" clearly indicate this.

And here is another stupid sentence from page 4-3. "we suppose
that this takes no energy because we do not change the height."
What does height have to do with energy on page 4-3, the whole
point is to derive the mgh formula from the impossibility of the
perpetual motion machine. This "reductio ad absurdum" method
is totally unfamiliar to me and I refuse to accept it.

Well, a novice would not be able to articulate these things clearly
but you know what I mean above. I suppose that most unprepared
minds would declare such teaching to be "garbage" and "vote with
their feet". Teaching an introductory physics in Feynman's way
would be another illustration that even the best things can be abused.
And a disgrace to a great teacher. I do not consider Section 4.2 to
be the answer to "how to introduce energy without work?".
Ludwik Kowalski