View Full Version : R: Torque or moment about a joint

Paolo De Leva
11-08-2007, 01:37 AM
Dear subscribers,

I believe that At Hof is right: this problem exists only in the English


"TORCHIO" (pronounced "tòrkio") exists in Italian, but it is not used in
physics (it is a "press" or "wine-press", a machine used to print or to
produce wine or olive oil...).

Actually, I discussed this topic in 2005 with John Paul and Jesus Dapena,
privately. Here's an explanation by Jesus (for those who don't know him: he
is a Spanish mother tongue Biomechanist, who studied biomechanics with Jim
Hay in Iowa University, USA, and now teaches in USA):

"...in Spanish the verb "torcer" (obviously closely related
etymologically to torque) means any bending, in any direction
whatsoever. It even applies to "bending a corner" in the street..."

"In Spanish, we also don't have a word like "torque". We have to use
"momento de fuerza", which I'm sure you understand. That is

As you see, Jesus loves the extended meaning of the word torque. I am sure
that nobody will be ever able to convince him to use the expression "moment
of a force". He has many good reasons not to accept your suggestion.

By the way, for the linear and angular momentum, both in Italy and Spanish,
we use the word "momento", exactly the same as for the moment of force:

Italian: "momento lineare" or "quantità di moto"
Spanish: "cantidad de movimiento"

Italian: "momento angolare" or "momento della quantità di moto"
Spanish: "momento cinético"

This is important because Italian and Spanish are the neo-Latin languages,
and "moment", "momentum", and "movement" come from a single Latin word:
"movimentum" (movimento in Italian and movimiento in Spanish).


Paolo de Leva

-----Messaggio originale-----
Da: * Biomechanics and Movement Science listserver
[mailto:BIOMCH-L@NIC.SURFNET.NL] Per conto di Altinus L Hof
Inviato: giovedì 8 novembre 2007 10.41
Oggetto: Re: 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. 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
9700 AD Groningen
The Netherlands

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