What you said would make a certain amount of sense for units but is not the accepted algebraic hierarchy for operators in mathematic. Perhaps as a result, it is not the accepted rule for units in either NIST or BIPM documentation. I dislike the negative exponents that they favor, and there is no good way to typ them in a browser. The only other choice is parentheses, $30/(kA·m). But compound units are not as complex as general algebraic statements. A rule of one solidus in a compound unit, all numerator units before it, all denominator units after it, each unit set off by space or raised dot would be AN acceptable rule. It just isn't THE accepted rule. --- On Fri, 4/10/09, Jeremiah MacGregor <[email protected]> wrote:
From: Jeremiah MacGregor <[email protected]> Subject: [USMA:44521] Re: Strange SI units To: "U.S. Metric Association" <[email protected]> Date: Friday, April 10, 2009, 10:14 AM Gene, $/kA.m can only mean dollars per kiloamp meter. Any unit to the right of the solidus (/) belongs to the denominator. If it is intended for the meter to be a part of the numerator, then the unit symbol would be: $.m/kA. Thus there is no need for brackets to group the symbols. Jerry From: "[email protected]" <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Wednesday, April 8, 2009 12:53:45 PM Subject: [USMA:44485] Re: Strange SI units A remaining objection is the "double operator" (/ then .) with ambiguous grouping: Is it "(30$/kA). m" or "30$/(kA . m)"? Conventional algebra is not strictly sequential as are many computer algorithms. Gene. ---- Original message ---- >Date: Wed, 8 Apr 2009 09:40:22 +1000 >From: Pat Naughtin <[email protected]> >Subject: [USMA:44467] Re: Strange SI units >To: "U.S. Metric Association" <[email protected]> > > Dear John and Ezra, > Two thoughts occur to me. > 1 How wonderful is the metric system? Here is an > obscure application — getting the electrical > energy form an off-shore wind energy source, and in > a matter of moments the engineers can derive an > appropriate unit, directly from the SI base units, > that is coherent and the best fit for this > application. > 2 Isn't it odd that the 'unit' for currency, dollar > (symbol $), was fitted to numbers at the front > rather than at the back; we write two dollars as $2 > rather than as 2 $. In the application that Ezra > found, it would make more sense, to me at least, if > it was written as 30 $/kA·m with all symbols after > the number. > Cheers, > Pat Naughtin > Geelong, Australia > On 2009/04/08, at 6:29 AM, John M. Steele wrote: > >It is a kiloampere-meter. > >It is an alternate way to express an amount of wire. To carry a given >current, a wire needs a certain cross-sectional area, but the area >depends on what the wire is made of. > >A way to equalize and express costs across wire types is to rate by >current carried, for each wire type that will require a certain area. >Multiplied by the length of the wire, that gives volume and should be >proportional to cost (at least fairly proportional).. > >However, I don't think I've ever seen it before. I had to read the >conext in the article to see what it is about. It is a clever way to >relate the cost of the wire to its mission (carrying current for a >distance) rather than purely by dimensions. > >It is analogous to looking at cost of fuels per unit of heat energy >rather than by volume or weight. >--- On Tue, >4/7/09, [email protected] <[email protected]> wrote: > > From: [email protected] <[email protected]> > Subject: [USMA:44462] Strange SI units > To: "U.S. Metric Association" <[email protected]> > Date: Tuesday, April 7, 2009, 3:46 PM > > Just came across this article: > > http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_62/iss_4/25_1.shtml > > but was flummoxed by this part: > > $30/kA·m > > What the heck is kA·m and why do they use it? > > Ezra > > Pat Naughtin > PO Box 305 Belmont 3216, > Geelong, Australia > Phone: 61 3 5241 2008 > Metric system consultant, writer, and speaker, Pat > Naughtin, has helped thousands of people and > hundreds of companies upgrade to the modern metric > system smoothly, quickly, and so economically that > they now save thousands each year when buying, > processing, or selling for their businesses. Pat > provides services and resources for many different > trades, crafts, and professions for commercial, > industrial and government metrication leaders in > Asia, Europe, and in the USA. Pat's clients include > the Australian Government, Google, NASA, NIST, and > the metric associations of Canada, the UK, and the > USA. See http://www.metricationmatters.com for more > metrication information, contact Pat > at [email protected] or to get the > free 'Metrication matters' newsletter go > to: http://www.metricationmatters.com/newsletter to > subscribe.
