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Re: Internal or external?



Brian McInnes wrote:
Here follows a "minor" point that I find irritating.

In the recent thread on treatment of Atwood type situations phrases
such as "each mass is acted upon by two forces" occurred from time to
time.  I think that we shouldn't confuse the property "mass" with the
name of the object.  I'd call it "object" or "body" or (better)
"block" but not "mass" or even "weight"

A kiloamen to that, Brian. Too often I find myself  trying to undo the confusion in my students' minds caused by such use of words and phrases in our textbook. Even calling the block a "body" usually gives rise to needless uncertainty, if not outright confusion.

We claim that our physics jargon helps avoid ambiguities and  misunderstandings, but many of us ain't consistent in that regard. We go along with the bastardization of our language in popular song lyrics and advertising, and we continue to use words in our teaching such as body rather than object, normal rather than perpendicular, curve rather than plotted line, constant rather than uniform, lab rather than experiment, and gas rather than gasoline.

We're equally careless when we use symbols. For example, why do we use F for most forces but then use f for frictional forces and N for the perpendicular force pressing two solid objects together?

To rephrase your example, if we refer to an object by its property of mass and an electrically charged object by its property of charge, why don't we refer to a moving object by its property of motion? "Here we have two speeds moving with the same velocity."

Keep preaching. Your congregation, though small, is with you, and some of us don't consider the points you raise to be minor.

poj
Collin County College