Dear Phil
Units can be interconverted if they differ only because of purely numerical
factors. Apart from such factors all units can be translated into a product
of a set of "base units" raised to various powers. In SI the base units are
metre m length
kilogram kg mass
second s time
ampere A electric current
kelvin K thermodynamic temperature
candela cd luminous intensity
mole mol amount of substance
Thus, for instance, a newton N is kg m s-2, a joule J=N m=kg m2 s-2 and a
pascal is Pa=N m-2=kg m-1 s-2. Dimensionally, Pa and J m-3 are equivalent.
K, degC and degF are all equivalent.
A practical way to see whether two units are equivalent is to try to use
udunits to convert between them.
$ udunits
You have: degF
You want: K
<K> = <degF>*0.555556 + 255.372
<K> = <degF>/1.8 + 255.372
You have: Pa
You want: J m-3
<J m-3> = <Pa>*1
<J m-3> = <Pa>/1
You have: K
You want: kg
udunits: Units are incompatible
Cheers
Jonathan
Received on Thu Nov 20 2008 - 11:58:29 GMT
