ingvar_johansson wrote:
>
> Here comes the only passage where the SI brochure mentions 'torque' (pp.
> 119-20):
>
> "In practice, with certain quantities, preference is given to the use of
> certain special unit names, or combinations of unit names, to facilitate
> the distinction between different quantities having the same dimension.
> When using this freedom, one may recall the process by which the quantity
> is defined. For example, the quantity torque may be thought of as the
> cross product of force and distance, suggesting the unit newton metre, or
> it may be thought of as energy per angle, suggesting the unit joule per
> radian."
>
> Ingvar (01)
Excerpted from my copy of ISO/DIS 80000-1, "Quantities and units"
-----------snip---------
3.2
kind of quantity
aspect common to mutually comparable quantities (02)
NOTES (03)
1 — The division of the concept ‘quantity’ into several kinds is to some extent
arbitrary.
EXAMPLES
a) The quantities diameter, circumference, and wavelength are generally
considered to be quantities of the same kind, namely, of the kind of quantity
called length.
b) The quantities heat, kinetic energy, and potential energy, are generally
considered to be quantities of the same kind, namely, of the kind of quantity
called energy. (04)
2 — Quantities of the same kind within a given system of quantities have the
same quantity dimension. However, quantities of the same dimension are not
necessarily of the same kind.
EXAMPLE
The quantities moment of force and energy are, by convention, not regarded as
being of the same kind, although they have the same dimension. Similarly for
heat capacity and entropy, as well as for number of entities, relative
permeability, and mass fraction. (05)
3 — In English, the terms for quantities in the left half of the table in 1.1,
Note 1, are often used for the corresponding 'kinds of quantity'. In French,
the
term “nature” is only used in expressions such as “grandeurs de même nature”
(in
English, “quantities of the same kind”). (06)
-----snip------ (07)
torque being "moment of force" (08)
n.b. - Units alone are not sufficient for determining "comparable quantities". (09)
jbc (010)
--
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Code 5583, Adv. Info. Tech.
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