Stan, Jim, and others, I agree, raised dots to denote multiplication of unit symbols, and solidi (slashes) to denote division of unit symbols are *optional*, and may be represented by spaces, or by the explicit power (positive or negative) of each respective unit symbol, as appropriate.
However, one must be careful to avoid the ambiguities (unspecified sequence order of operations) of certain mixes of multiplications and divisions of unit symbols. I like the flexibility of being able to use any of these three methods of expressing combinations of unit symbols in SI, without exclusion of the other two methods. There is no CGPM resolution or BIPM position statement that I know of that favors one of these three methods over the other two, unless by the example of printed documents. Eugene Mechtly. On Dec 17, 2014, at 9:10 AM, Stanislav Jakuba <jakub...@gmail.com<mailto:jakub...@gmail.com>> wrote: In due respect, Gene, there is no need for the alternative W.s as there is no need for the N.m (for work) or the kg.m2/s2. Associating any quantity with only one form of its unit represents a major advantage of SI. Let's stick with it. The joule is the only form for the unit of energy to be used in practice. To those who commented on this email, and I thank you all, you should know that the Editor "bought" the reasoning and plans the article for the January issue. Stan Jakuba PS: While on this topic, the above principle applies also to the quantity "energy consumption" that is universally expressed, wrongly, as Btu/day, MWh/year, etc. In the spirit of SI, the ONLY unit for power is the W. And because energy consumption is a flow, the unit of power (W) is correct here despite the almost universal, worldwide opposition. Imagine that "... per day, per year, per hour, per minute, per decade ..." all gone with the watt. Suddenly all statistics are comparable directly. On Mon, Dec 15, 2014 at 11:58 AM, mechtly, eugene a <mech...@illinois.edu<mailto:mech...@illinois.edu>> wrote: Stan, The “joule” of energy equals exactly one “watt.second”; the product of the watt and the second, where all reasonably literate persons have heard of the watt and the second, and might even know that the watt of power is *defined* as one joule per second for the time rate of energy processing or transfer. Try using the watt.second (Ws or W.s) in your writings, until your readers are more familiar with the joule. Gene Mechtly. On Dec 15, 2014, at 8:17 AM, Stanislav Jakuba <jakub...@gmail.com<mailto:jakub...@gmail.com>> wrote: USMA members will, I hope, be pleased reading the answer to an editor who desired that American units be presented alongside the SI values in my manuscript. Dear .... I attempted the parenthesis you suggested but found the resulting complexity of the text disruptive and harder to read. And there are other problems associated with doubling each unit. Allow me a few words of explanation. The article is about comparing two sets of numbers. For that, there need not be any unit at all. The majority of readers will skip the units anyway, and the few curious engineers and physics teachers will know how to convert to whatever units they like. As to the several common values I doubt that there are readers that wouldn't know that water freezes at 0 deg. Celsius or what a km is. As to the substitution for the one still unfamiliar unit – the joule or MJ – here Americans use several different units for energy such as calorie, Btu, kilowatt hour, lb-ft. As a result. I am at a loss which one to select. Different professions use them all – that would be four parentheses. Instead, I spelled out the symbol MJ and use it consistently thereafter. Thus no problem with comparing numbers. In any case non-technical readers will not care, and experts who might be checking the math will convert the value to whichever unit they like. I am pleased to say that, up to now, no publisher asked me to add conversions. Dozens of articles, no complains. May I say that one might underestimate one’s readers? As a side issue, you may be interested in why I insist on the units of a system that has only one unit for any measurement, be it energy, power, or length. That’s because, with the multiplicity of the U.S. energy and power units, it is common to present false or misleading numbers and get away with it for it is too difficult and bothersome for readers to look up all the conversion factors to check. I might also point out that since it is the Federal Law and Exec. Order that state that "SI metric is the preferred measurement system in the U.S." my writing in SI only should help citizens learning it. Once they see how easy comparisons are with SI units, they might actually prefer that system particularly when noticing the cheating in the daily press with American units such as the one illustrated in the other enclosed treatise. Yours, Stan Jakuba
