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Re: centrifugal force (cont)



On Friday, Dec 13, 2002, at 10:31 US/Eastern, Justin Parke wrote:

I'd like to hear a fictitious dialogue between a professor and
a thoughtful student where the professor is explaining the
difference in viewpoints we are discussing here.

This is the way the conversation usually goes with me...
(the student may not be "thoughtful" but it is the usual kind
of student I get)

Professor: We need to predict the motion of objects on the surface
of the earth. Objects that are stationary with respect to the
surface are moving around the axis with the earth. Consequently,
there must be a centripetal force exerted on the object.

Student: Excuse me, but in physics I learned that there is
no such thing as a centripetal force.

Professor: Do you mean centrifugal force?

Student: Maybe. What's the difference?

Professor: "centripetal" means "toward the center" and
"centrifugal" means "away from the center".

Student: OK. I guess it was "centrifugal" then. There
is no such thing as a centrifugal force.

Professor: Why?

Student: I don't know - that is just the way it is.

Professor: Maybe it is that in a rotating
reference frame there appears to be a centrifugal
force acting that does not appear to be acting in
an inertial reference frame.

Student: Yeh - that's it.

Professor: Well, here we find it is much simpler to
solve the problem in our rotating reference frame so
we will include the centrifugal force.

Student: No - you can't do that - there is no such thing.

...etc.

____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; 570-422-3428; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ., E. Stroudsburg, PA 18301