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Re: Dr. Rassoulian's comment.

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  • Re: Dr. Rassoulian's comment.

    I found Dr. Rassoulian's earlier comment regarding the lack of interest in
    his previous post interesting.

    I would actually find the listserv far more valuable if there were more
    posts discussing the projects people are working on, eliciting comments on
    them, working through problems collectively, refining future projects, and
    so on.

    While I understand that posts about the minutiae of particular
    instrumentation or open positions serve a clear purpose, they are likely
    less instructive to the group as a whole. Discussing problems or research
    projects is something we can all benefit from.

    That's my two cents.

    Frank Washko

    -----Original Message-----
    From: * Biomechanics and Movement Science listserver
    [mailto:BIOMCH-L@NIC.SURFNET.NL] On Behalf Of Ton van den Bogert
    Sent: Thursday, November 08, 2007 2:37 PM
    Subject: [BIOMCH-L] one more...

    Paolo de Leva submitted this long posting while my moderator's message was
    still being processed, so it would be cruel not to distribute it. Paolo
    always has a great multicultural and historical perspective.

    But please, no more after this.


    Ton van den Bogert, Biomch-L co-moderator

    > -----Original Message-----
    > From: Paolo de Leva []
    > Sent: Thursday, November 08, 2007 4:04 PM
    > To: BIOMCH-L
    > Subject: R: Torque or moment about a joint
    > Dear subscribers,
    > Ton van den Bogert is right: "it would be great if we could
    > agree on this".
    > However, in this case we have two separate and widely
    > accepted standards.
    > Standards, not opinions. There has been a widely known
    > precedent: SI (Systeme International d'Unites) versus the
    > British system. Forgive me for the lack of detail (I am
    > swamped of work right now):
    > 1) The SI was born in the 18th century; its mother was the
    > French revolution, it became adult in the late 20th century.
    > 2) Today it is not yet completely accepted in US, but it
    > will. May be in 10, 50, 100 or more years, but it will.
    > Indeed, nobody can honestly deny that the SI is the best
    > system, not even those who keep using a different system.
    > They do so just because they are used to. The change is too
    > expensive for
    > them: a desired good that they cannot afford to buy.
    > 3) I am not going to compare BIOMCH-L with the France of the
    > 18th century.
    > This is not the point.
    > 4) The point is that "torque" versus "momentum" is a war that
    > nobody can win. Both standards have strong weaknesses! (see
    > for instance the etymological notes in my previous messages).
    > 5) To win a war, a third, less questionable name is probably
    > needed. For
    > instance:
    > - "rotor" (if John Paul says that a torque produces only torsion,
    > please indulge me and let me say that a rotor can produce any
    > kind of rotation :-), or
    > - "angular force" or "rotational force", as opposed to "(linear)
    > force" (notice that Joseph Louis Lagrange introduced in the
    > late 18th century the "generalized force", 6 numbers including
    > force and force moment).
    > 6) Too many students learn physics in USA, or studying
    > textbooks written by US physicists (including international
    > students). The influence of USA universities on the
    > scientific community is terrific.
    > 7) Do we know how many scientists (not only biomechanists)
    > are used to use or chose to use the word torque as a synonym
    > of moment in their studies (including physicists)?
    > 8a) I suspect that "moment" was the word initially used by
    > everybody. My guess is that "Torque" was adopted by
    > physicists (probably stealing it from
    > engineers) to substitute moment, because they did not like
    > the aspecificity and ambiguity of the word "moment" (it comes
    > from "movimentum", it also means "instant"; what has that got
    > to do with rotation?). This change was intentional, not casual.
    > 8b) There was also another change, which is probably related:
    > Newton called "quantity of motion" the quantity that we now
    > call (in English) "linear momentum" (Italian: "quantità di
    > moto"; Spanish: "cantidad de movimiento").
    > And "moment of the quantity of motion" the quantity that we
    > now call "angular momentum". Not difficult to imagine that
    > the change was welcome!
    > Again "quantity of motion" is too generic. As you see, the
    > rationale is similar.
    > 9) Notice that the SI prescribes the name of the unit
    > ("Newton metre"), but as far as I know it does not give a
    > preference about the name of the quantity ("moment of force"
    > or "torque").
    > 10) An optimistic observation: at least this is not a very
    > expensive change.
    > A new non-questionable name for this quantity may be accepted
    > faster than the whole SI. There is no need of a revolution.
    > 11) Pessimistic: possibly, other terminological "fixes" are
    > needed in other chapters of physics. They won't accept a
    > change in a single word, if other questionable words exist. A
    > representative international committee (ISO) is the only
    > organization that can solve this problem. And most likely,
    > the committee will be mainly composed of physicists.
    > In short: it does not matter if we agree on using the word
    > "moment". We are not going to convince the other half of the
    > word. Terminology evolves, but changes are expensive and
    > nobody will ever accept questionable changes.
    > Etymologically, "moment" is a questionable word. Moreover, I
    > suppose that the river of history is flowing in the opposite
    > direction! We are just advocating a return to the past. We
    > are not starting a revolution, but resisting against a
    > revolution started a long ago.
    > With kind regards,
    > Paolo de Leva
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