deka (da) = 10 x base unit (ex. 1 dag = 10 g) deci (d) = 0.1 x base unit (ex. 1 dm = 0.1 m)
Decimeters are also encountered in science, where they tend to be a convenient unit for some applications. One of the most common uses of the decimeter is dm^3, which is of course 1 L. Remek On 1/24/07, David King <[EMAIL PROTECTED]> wrote:
I thought that 10 of something used the prefix deka, not deca. Or are both permissible? David King Bill Hooper wrote: > > On 2007 Jan 21 , at 9:48 AM, [EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]> wrote: >> I might be mistaken with my views of proper metric usage yet I fell >> the need to share the embarrassment of asking if there is a place >> held in the proper Si metric system that includes Decimeter. > > Tim, > > Yes, SI does include the decimetre. > > The SI metric system has a basic unit for every type of measurement > and a series of prefixes used to form larger and smaller units. The > officially recognized and sanctioned prefixes DO include "deci-" which > may be appended to any basic unit to form a unit which is one tenth as > big as the basic unit. Thus, for example, it can be used with "metre" > to make "decimetre" where: > > one decimetre = one tenth of a metre, or 1 dm = 0.1 m > > Of course these relations can be reversed. So, we can write: > > one metre = ten decimetres, or 1 m = 10 dm > > It is often easier to discuss these things in this second form since > it does not involve fractions. > > However, most of the prefixes in the SI metric system are used to make > new units that are 1000 times as big as the next smaller unit, not > just 10 times. To illustrate some of the more common prefixes, and > using "metre" as the base unit for example, we have: > 1 gigametre = 1000 megametres > 1 megametre = 1000 kilometres > 1 kilometre = 1000 metres > 1 metre = 1000 millimetres > 1 millimetre = 1000 micrometres > 1 micrometre = 1000 nanometres > etc. > > In the earliest forms of the metric system, there were also prefixes > for every step-of-ten. There were only six at that time. Using "metre" > as the base again: > 1 kilometre = 10 hectometres > 1 hectometre = 10 decametres > 1 decametre = 10 metres > 1 metre = 10 decimetres > 1 decimetre = 10 centimetres > 1 centimetre= 10 millimetres > > However, having a new prefix for EVERY factor of ten soon proved to be > too cumbersome. As the metric system was used for larger and larger > things (distances to stars) and smaller and smaller things (masses of > protons and electrons) there would need to be too many prefixes for > convenience. At some point the decision was made that, when adopting > additional new prefixes, only powers of 1000 would be used. > > Since that time, one finds that in most areas, ONLY the powers of 1000 > are used. However, hecto-, deca-, deci- and centi- ARE STILL A PART of > SI and there are a number of areas in which some of them are in quite > common use. > > The prefix "centi-" is in very prevalently use as the "centimetre", of > course, although there are efforts in some parts of the world > (Australia, for example) to eliminate it and use millimetres > instead. In Europe it is not uncommon to find wine and beer served by > the centilitre or the decilitre. > > The land area unit, "hectare", while not itself an SI unit, is defined > as 1 square hectometre and the liquid volume unit, "litre" (also not > an SI unit itself) is defined as 1 cubic decimetre. There are other > examples. > > However, generally, there is a tendency to gradually eliminate the use > of the old power-of-ten prefixes in favor of using just power-of-1000 > prefixes. Many people would agree, at least, not to introduce the > power-of-ten prefixes into situations where they are not already > traditionally used. Others would like to see them phased out even in > those traditional uses. While some people vehemently protest any > effort to eliminate those power-of-ten prefixes, others are ardently > in favor of doing just that. Time will tell. > > I hope this answers your question and gives you some context for > understanding how the decimetre is (or is not) used. > > > Bill Hooper > 1810 mm tall > Fernandina Beach, Florida, USA > > >
