Firstly, nobody here recommends using km/hr, simply because it's km/h. (h, and only h, is the SI symbol for hour.)
Secondly, days (d), hours (h) and minutes (min) ARE units in use with SI and their use is NOT deprecated in the SI Brochure or in IEEE/ASTM SI 10. As defined for the purposes of SI, all three (including day) are exact multiples of the second. So is week, but there is no official SI symbol for it. Kilometers per hour (km/h) is used for travel purposes, because it relates well to the dynamics of an actual journey and because people can have a feel for it. The only real alternative would be meters per second (m/s), which works well for wind speed and should work well for the speed of a baseball and many other non-travel-related movements, but is not very useful to someone traveling from one city to another. Bill Potts, CMS Roseville, CA http://metric1.org [SI Navigator] >-----Original Message----- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] >Behalf Of Gavin Young >Sent: Wednesday, February 18, 2004 09:54 >To: U.S. Metric Association >Cc: U.S. Metric Association >Subject: [USMA:28765] Re: second based on decimal day > > >If hours are not considered a derived unit of the SI second and >thus a part of >SI, then why does the USMA and SI promote using kilometers/HOUR (km/hr) in >place of miles/hour? If the hour is not considered a derived SI >unit, then the >USMA and SI should be promoting only saying kilometers/SECOND or >meters/SECOND - > instead of promoting use of the term kilometers/HOUR!!!! > >Why does the USMA tell people to use km/hr for road signs if the >hours are not >considered part of SI??? If hours are not a part of SI, then you are not >following your own admonitions when you use the USMA server to >promote use of >the term km/hr. Hence the inconsistency of the time units being >promoted by >USMA and and many SI promoters, thus the need for decimal (aka >"metric") time >units! If the inconsistency or flaw of using hours does not exist >in SI, then >it exists in those who are promoting the use of the term >kilometers/HOUR as a >part of proper SI usage!!! > >Lets fix the SI system by using decimal time units, or at least >insist on using >m/s instead of km/hr!! > >Quoting Bill Hooper <[EMAIL PROTECTED]>: > >> [EMAIL PROTECTED] wrote: >> > ... you seem to prefer to swallow up (or put up) with this clear flaw >> > in the SI system >> >> Sorry, but days, hours and minutes are not part of SI and have never >> been intended to be. They do not represent a flaw in SI. If anything, >> they represent a flaw in the way we measure the time of day. The uses >> to which scientific and technical time measurements (and units) are >> used are so different from the ways in which time of day is used that >> there does not seem to be any reason why the two need to be (or can be) >> coordinated or reconciled. >> >> It's not a flaw in SI because it is not part of SI at all, and >> therefore is not of much interest to proponents of SI (many of whom are >> members of USMA and subscribers to this list). >> >> Regards, >> Bill Hooper >> Fernandina Beach, Florida, USA >> >> > > >Gavin Young >http://www.xprt.net/~hightech , http://www.renewableelectricity.com, >http://www.electric-automobile.com >
