Re: impulse/momentum

[Jack Uretsky <jlu@HEP.ANL.GOV>]

        Jim, you are really raising a number of points here.  A decade ago
I decided to get a high school teaching certificate; as part of the course
I student-taught at a local high school.  The chair, who was my suprvisor,
had been running a very succussful program requiring 3 physics teachers
plus others for the so-called physical science courses.  He was very
critical of my opening remarks, which were somewhat along the line you
suggested.  His criticism, possibly well-based, was that young students
don't want to be told that they're not getting the best, the latest, and
the most blessed that the educational system has to offer.  So my answer
to your question "Can't we say...?" is: I don't know.  At some point the
interested student is going to find out what is being offered in the big
tent.  Don't give him/her more than it wants to know.

        As to the stationary turbine blade, they do happen in real life,
quite by accident.  The problem is - among other things - an exercise in
reading which apparently wiped out some members of this list.  I am very
much in favor of problems with distraction elements and unexpected
conditions because they promote thoughtful, rather than rote, responses.

I don't find your diparagement of problems that you don't like as "cartoon
physics" very helpful.  As a matter of fact, my favorite cartoon often
does very good physics - I occasionally see clips on office doors here at
Argonne.
                                        Regards,
                                                Jack


On Sun, 14 Dec 2003, Jim Green wrote:

> >         What we are endeavoring to teach - no! What we are endeavoring to
> > make available to the students is the opportunity to attack problems that
> > they have never seen before, because that is what they will be doing in
> > real life.  We can model for them how we attack such problems, but the
> > actual solutions are irrelevant.
>
> True enough, Jack, but there is no need of camouflaging reality.  Can't we
> say as we approach Newton's Laws with an introduction that explains that
> Newton only deals with slow speeds ie common speeds Ie only those that are
> everyday -- and it does this quite well -- but that later in physics
> education we will deal with faster speeds and then Newton doesn't work.
>
> Or as the ice skater pushes off the wall, we might say that we are going to
> assume that the wall is fixed, but that after we get into the problem we
> will see that this assumption will cause a violation of Newton and we will
> need to explore another ramification.
>
> It seems to me that teaching Cartoon Physics is counter-productive.  It is
> easier at times at first but it confuses the hell out of the students later
> -- and then the teaching is more difficult.
>
> In a turbine it is silly to propose that the blade doesn't rotate and
> confuse the physics to the cartoon level.
>
>
> Jim Green
> mailto:JMGreen@sisna.com
> http://users.sisna.com/jmgreen

--
"Don't push the river, it flows by itself"
                                Frederick Perls