Terry Simpson asked in USMA 23981
Gene Mechtly wrote:
Ton = 1 000 kg is a well established definition of ton in most
countries (spelling variations aside), and is more explicitly related
to the SI base unit of mass, kilogram, than is megagram.
The Mg is unnecessary and is more of a deviation from coherent SI.
I don't understand. Despite the kilogram being the base unit, the names
are manipulated as if the base unit were the gram. Part of the true SI
sequence for mass is:
pg picogram
ng nanogram
�g microgram
mg milligram
g gram
kg kilogram
Mg megagram
Gg gigagram
The tonne is a table 6 unit and is therefore non-SI but 'accepted for
use'. So it is acceptable to have:
�t microtonne
mt millitonne
t tonne
kt kilotonne
Mt megatonne
Gt gigatonne
I have seen tonne and larger multiples such as kilotonne. However, I do
not regard these as anything other than commonly used non-SI anomalies.
Are you suggesting that the normal SI prefixes should not apply for
mass?
I am with you, Terry. There can be no excuse for microtonne and
millitonne. The kiloton and megaton are only used for designating
atomic weapons and always as "TNT equivalent". Those can not be
considered as metric units, but only as military jargon.
--
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
