Re: Being careful with dimensions

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Wed, 22 Sep 1999, Michael Edmiston wrote:

> ... if you routinely write F = (2i - 3j) N, would you also write F =
> (3.61 at -56.3-degrees) newtons?
>
> I would not typically write that.  I would write F = 3.61 N at -56.3
> degrees.

I would as well, again for the sake of economy, but I see absolutely
nothing wrong with the former and even rather like it for the point it
makes about the algebraic nature of units.

This does, however, remind me of another of my pet peeves.  (Boy, do I
have a lot of them when it comes to units!)  I intensely dislike the
common way of expressing experimental results as, for instance,
"4.8 +/- 0.2 cm" because one cannot add (or subtract) a length to (or
from) a number.  One should write either "4.8 cm +/- 0.2 cm" or
"(4.8 +/- 0.2) cm".  I prefer the latter because of its economy.  One
could express the same result as "(4.8 +/- 4%) cm" but I prefer
"4.8 cm +/- 4%" again purely for reasons of economy.

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm