Re: kinematics language

["Daniel S. Price" <dprice@JEFFCO.K12.CO.US>]

Thank you, Mr. Titus, for addressing the terminology issue.  Each year, and
this year in particular, I have taken great pains to eliminate terms which
carry multiple meanings in both the vernacular and in more "technical
settings."

> I suggest never using the word "deceleration".  If one means, slowing
> down, then I suggest saying "slowing down".  If one means, an
> acceleration in the -x direction (or along whatever axis), then say
> that.  If one means, an acceleration that is opposite to the
> velocity, then say that.  Deceleration is often used with different
> meanings. It's no wonder students are confused.

I have found this to be entirely true, and have not introduced the term
'deceleration'.
When students use it (familiar as they are with automobiles), I encourage them
to restate their meaning.  [Do they mean "slowing down" or "accelerating in
the negative direction"?]

> The words "increasing" and "decreasing" can be confusing if one isn't
> careful to distinguish between the magnitude of a quantity and the
> quantity.  I use this example in my class: If your checking account
> is in overdraft protection with a balance of -$400 and you deposit
> $300, has your balance increased or decreased? <increased>  Has "how
> much you owe the bank" increased or decreased? <decreased>

This year, I have made every attempt to expunge "increase" and "decrease" from
my discussions for the exact reason you cite:  magnitude versus direction.
Referring to values as becoming "more positive" or "more negative" is a bit
awkward (right now, anyway) but provides apt descriptions, and, I hope, will
lead to better understanding.