Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Kinematic equations (Was: Crib Sheets)

Good question. Here's the problem. Consider the atwood machine. An analysis
has little g all over the place, yet nothing is accelerating at that rate.
So, in that context (and all contexts except freefall without air
resistance) to call little g an acceleration is misleading.

I once watched a civil engineer hold up a pendulum (motionless) and
interrogate a student with "and what's the acceleration here? There's an
acceleration here!" The student was rightly confused, for the bob's
acceleration was zero, and the CE prof was looking for little g.

At 09:09 PM 3/31/96 GMT, you wrote:
*Re: Kinematic equations (Was: Crib Sheets) *
John Gastineau wrote on Sat, 30 Mar 96 13:07:23 -0500 :

We don't help our students very much by our use of language. How often do
our students hear "the acceleration due to gravity" in the context of little
g? We use units of acceleration on it, too, so it MUST be "the"
acceleration! We're our own enemies.

I have taken to telling my students to "watch their language" when they use
such phrases. Little g is more properly called the local gravitational
constant, and it has a value of 9.8 N/kg, not 9.8m/s^2.

And once again I have to ask: Where is the problem? Maybe I'm
used to my terminology too much, but to me 'g' is an
acceleration: When I let a body fall (air removed) it IS
accelerated with a~9.8 m/s^2. This value *describes* what happens
(and in what way), it doesn't give a reason why.

Bye, bye
+please correct me, if I misuse some technical terms+
Guntbert Reiter, Graz, Austria
e-mail :

PLEASE do not reply to the email address in the header of this message; use
the address instead.

John E. Gastineau PV34PV3P
North Carolina State University Physics
Physics Courseware Evaluation Project
Box 8202
Raleigh, NC 27695-8202

919 515 7059 voice
919 515 2682 fax