View Full Version : Re: Torque or moment ? about a joint

Adrian Smith
11-08-2007, 12:18 AM

The Oxford English Dictionary has TORQUE (noun):

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

Adrian Smith
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
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
- Chaffin & Andersson
- 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.
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
9700 AD Groningen
The Netherlands

tel. (31) 50 363 2645
fax (31) 50 363 3150
e-mail a.l.hof@med.umcg.nl