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Re: impulse/momentum



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