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11-08-2007, 01:30 AM
Also from OED:

MOMENT (noun)

Any of various functions describing torsional effects, generally having
the form of the product of a force and a distance; spec. the turning
effect produced by a force; the magnitude of this, equal to the product
of the force and the perpendicular distance from its line of action to
the point about which rotation may occur.
moment of a couple [cf. French moment d'un couple (1869)], the product
of either of the two equal forces comprising the couple and the
perpendicular distance between their lines of action.

Etc etc

-----Original Message-----
From: * Biomechanics and Movement Science listserver
[mailto:BIOMCH-L@NIC.SURFNET.NL] On Behalf Of Adrian Smith
Sent: 08 November 2007 14:18
To: BIOMCH-L@NIC.SURFNET.NL
Subject: Re: [BIOMCH-L] Torque or moment ? about a joint

www.oed.com

The Oxford English Dictionary has TORQUE (noun):

"The twisting or rotary force in a piece of mechanism (as a measurable
quantity); "the moment of a system of forces producing rotation."

Leeds University Library
+44 (0)113 3435531

-----Original Message-----
From: * Biomechanics and Movement Science listserver
[mailto:BIOMCH-L@NIC.SURFNET.NL] On Behalf Of Altinus L Hof
Sent: 08 November 2007 09:41
To: BIOMCH-L@NIC.SURFNET.NL
Subject: Re: [BIOMCH-L] Torque or moment about a joint

Dear All,
That is an interesting discussion, indeed, about possible differences
between moment and torque.
To a great extent this is a 'jam or marmelade' discussion. It just
happens that English has two words for (about?) the same thing.
I have the privilege to teach biomechanics in the Dutch language, and
Dutch has the word and concept 'moment' but no equivalent of 'torque'.
For all I know it is similar in German (and other languages?). The
problem is then, when students are to write something on mechanics in
English, they ask which of the two terms to use. My answer is: the
meaning of both words is the same, but you better use 'moment'.

In English or US textbooks as a rule one of either term is used, and it
is stated that both terms are equivalent. A quick scan of my bookshelf
showed that 'torque' is used by
- Hamill & Knutzen
- Kreighbaum & Barthels
- Mc Ginnis
And 'moment' by
- Winter
- Tozeren
- Robertson ('Introduction..')
- Robertson et al. ('Research methods..')mostly
- Hibbeler (engineering text)
- Prentis (,,)
- Zatsiorsky (Kinetics of human motion)

The latter reference, for me in difficult cases the ultimate authority,
suggests to reserve the term 'torque' for the moment of a couple ( p.
19).
The special thing of such a moment is, that it is a free moment and does
not depend on the location of the axis with respect to which it is
calculated, different from the moment of a single force.
In the example of Young-Ho Kwon: with a screwdriver you apply a torque,
with a spanner you apply a moment to the screw or bolt. In biomechanics
therefore, in my opinion 'moment' is in 99% of the cases the correct
term, and no major misunderstanding will result if it is used in the
remaining 1%.

At Hof
Center for Human Movement Sciences
University of Groningen
PO Box 196