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Re: g



The sign is of course arbitrary, depending upon how you are orienting the
coordinate axes to which you are refering the measurements.

What's not arbitrary is that it is "down" as you say. It strikes me that
the problem is precisely the problem of understanding the difference between
velocity and acceleration. I'd suggest looking at Arons book section
2.7,2.8 and 2.9 in "Teaching Introductory Physics".

Joel

-----Original Message-----
From: Tina Fanetti [mailto:FanettT@QUEST.WITCC.CC.IA.US]
Sent: Monday, September 10, 2001 1:24 PM
To: PHYS-L@lists.nau.edu
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