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Re: [Phys-l] Deceleration or Negative Acceleration



I don't like either term. In our usage, accelerations in the direction of motion cause object to increase speed while accelerations opposite the direction of motion cause objects to decrease speed. Accelerations at right angles to the direction of motion cause a change in direction. Accelerations at any angles other than 0, 90,180,270 are dealt with by breaking the motion into orthogonal components and analyzing the accelerations along each of those directions with the above rules.

All of that is a mouthful and requires some considerable effort to ingrain, but it eliminates a lot of other problems, not the least of which is the freedom to choose positive/negative directions in any particular situation/problem.

my 20 ml worth of gasoline! ;-)

Rick

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Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN
rtarara@saintmarys.edu
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Free Physics Software
PC & Mac
www.saintmarys.edu/~rtarara/software.html
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----- Original Message ----- From: <pschoch@nac.net>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Tuesday, September 09, 2008 10:02 AM
Subject: [Phys-l] Deceleration or Negative Acceleration


I instituted the use of "Reading Questions" in my classes this year, and I
am getting some of the most interesting questions this semester from my
students.

This is one that I've not run into before... A student has asked which is
proper terminology: "Negative Acceleration" or "Deceleration".

Of the textbooks on my shelf, about half are for the first and the other
half seem to use both interchangeably. Interestingly, those that say
"Negative Acceleration" is the proper term are all of a more recent
vintage.

Is one or the other really more used/acceptable?

Thanks,
Peter

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