Roxul Industrial Insulation Process - Manual (Page 138)

Unit
s, c
onv
er
sion f
act
or
s and t
abl
es
3.1.5 SI units
The International System of Units, also referred
to as SI (Abbreviation for French: Système
International d’unités), embodies the modern
metric system and is the most widely used units
system for physical units. The system was
originally established in response to demands
from the field of science and research, however it
is now the prevalent units system for the
economic, technological and trade industries. In
the European Union (EU) and the majority of other
states, the use of the SI units system in official
and business transactions is prescribed by law;
however there are many national exceptions to
this rule.
SI Base units
The SI units system is composed of seven base
units. In order to use the base units for
applications involving different scales, certain
prefixes such as Kilo or Milli are used. These are
also used in conjunction with derived units and,
to some extent, with units from other systems.
3.1.6 SI derived units with special
names
In addition to the base units, the International
System of Units also includes derived units, which
are made up of one or more of these base units
by means of multipli cation or division. The clearly
defined product of powers of the base units are
not referred to as a dimension of the physical
size as such, but rather the system is formally
structured in that way. It is possible for example to
express areas in terms of meters square (m²) or
speeds in meters per second (m/s).
Some of these compounded units are assigned
names and symbols, which can even be combined
once again with all of the base units and derived
units. The SI unit “force” for example, the Newton
(1 N = 1 kg m/s²), lends itself to express the unit
“energy”, the Joule (1 J = 1 kg m²/s²), which is
equal to the equation Newtons multiplied by
meters. The following 22 derived units have their
own name and unit symbol.
Notable US units are given in an additional table.
Basic unit
Dimension
Symbol
Quantity
(metric)
Unit
(metric)
Quantity
(US)
Unit
(US)
Length L Meter m Feet ft
Mass m Kilogram kg Pound lb
Time t Second s Second s
Electric current I Ampere A Ampere A
Thermodynamic temperature T Kelvin K Rankine R
Amount of substance N Mol mol Mol mol
Luminous intensity J Candela cd Candela cd
135