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Re: impulse/momentum



Hi Jim-
You ask, what did you miss? Well, for one thing you forgot about
your uncle Nedvort, who forgot to oil the the turbine and then went off
and got drunk in the Catskill's and when he woke up twenty years later and
statrted up the turbine the rotating gismo was frozen solid to the the
walls of the stationary thingumbob and when he beent over to wash his face in
the gently splashing water, as was his former habit, the stream hit him in
the face and knocked him on his hindquarters and he wanted to know how
come.
The other thing you forgot is that physicists, and, to a lesser
extent, engineers, try to understand the world around them by dealing with
solvable idealizations that are only rough approximations to the real
world. That is one of the great lessons that we can teach our students
and one of the intellectual habits that distinguishes us from business
types who evaluate every transction with penny precision, whether such
precision is or is not a plentiful waste of time.

Regards,
Jack
On Sat, 13 Dec 2003, Jim Green wrote:

This one is from Halliday Resnick and Walker, problem 10.17, which I
quote: "A stream of water impinges on a stationary 'dished' turbine blade.

Another puzzlement I see here is why would the turbine blade be
stationary? Isn't the whole point of the machine to have the turbine blade
rotate? Further there isn't a chance that the water/bladed collision would
be elastic in any case. In a real case the water impacts the blade and
does work on the blade -- The blade does work on the water -- the water
heats up and slows down.

I don't see the point of this comic book question.

What did I miss?


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen


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