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Re: g



Try some simple kinematics problems where YOU choose down to be the positive
direction.
Maybe do the same problem twice, once with each sign convention. Stress
that there is no intrinsic sign with any vector quantity, but rather, the
sign convention is set by the person solving the problem and their choice of
coordinate systems.

Rick

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Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

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----- Original Message -----
From: "Tina Fanetti" <FanettT@QUEST.WITCC.CC.IA.US>
To: <PHYS-L@lists.nau.edu>
Sent: Monday, September 10, 2001 1:23 PM
Subject: g


Hello
I have a problem with my calc-based physics students. The problem is over
the sign of g, the gravitational acceleration.

I have told them the convention is that it is always downward even if the
object is going upward.

I can't seem to explain to them why this is. They tell me the book says
it is positive. That is not what the book says, the book says exactly what
I am saying.

How can I make it clearer to them about g and its sign?

Thanks
Tina

Tina Fanetti
Physics Instructor
Western Iowa Technical Community College
4647 Stone Ave
Sioux City IA 51102
712-274-8733 ext 1429