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627:"In practice, with certain quantities preference is given to the use of certain special unit names, or combinations of unit names, in order to facilitate the distinction between different quantities having the same dimension. For example, the SI unit of frequency is designated the hertz, rather than the reciprocal second, and the SI unit of angular velocity is designated the radian per second rather than the reciprocal second (in this case retaining the word radian emphasizes that angular velocity is equal to 2pi times the rotational frequency). Similarly the SI unit of moment of force is designated the newton metre rather than the joule."
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688:"In the interests of clear teaching, the convention (which I am glad to see has been adopted in America) has been adhered to throughout, of using the word âpoundâ when a force is meant, and âlb.â when a mass is meant, and I have ventured to give the name of a âslugâ to the British Engineerâs Unit of Mass, i.e. to the mass in which an acceleration of one foot-per-sec.-per-sec. is produced by a force of one pound.'
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separation of their units of measure, as can be seen on all the
Knowledge pages still using "Nm" as a symbol for newton-meters, and due to the fact that before SI, "gm" was an acceptable symbol for grams, there would be ambiguity that would need to be resolved if kilogram-meters were used. Is "kgm" the symbol for kilograms, or for kilograms multiplied by meters&that's the question people would have to ask.
624:"A derived unit can often be expressed in different ways by combining the names of base units with special names for derived units. This, however, is an algebraic freedom to be governed by common-sense physical considerations. Joule, for example, may formally be written newton metre, or even kilogram metre squared per second squared, but in a given situation some forms may be more helpful than others.
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The symbol for torque should be upper case gamma for the following reasons: 1. It looks like a handle. Something one can turn 2. Lower case tau is used for other things 3. Upper case gamma is not used for anything else in introductory physics courses. 4. American students recognise upper case greek
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page, I assumed "ft.lbf" was a typo, but I see now that it's actually a pretty common way of abbreviating "foot-pounds". It would be somewhat difficult for someone who knew little of US units to figure this out, since no search on
Knowledge ("ft¡lbf", "ft.lbf", "ft lbf", and so on) will actually get
745:
It is my impression that when it comes to automobile engine torque, the foot first versions predominate, pretty much everywhere (even as ft-libras and the like). But you will find variations among different manufacturers, variations among different magazine editors, etc., and in large groups little
675:
In the
Gravitation or Engineerâs system in this country, which starts with the foot and second as units of length and time, and the pound pull (i.e. the earthâs pull on the standard lb.) as unit of force, the unit of torque is that of a couple of which each force is 1 pound and the arm 1 foot. This
667:
Since in the
British absolute system, in which the lb. is chosen as the unit of mass, the foot as unit of length, and the second as unit of time, the unit of force is the poundal, it is reasonable and is agreed that the British absolute unit of torque shall be that of a poundal acting at a distance
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As I pointed out above, and as you can determine for yourself by searching the internet with your favorite search engine, when kilograms-force are used, the "meter-kilogams" order is more common than the "kilogram-meters" order (perhaps in part due to he tendency of people to be sloppy in the
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seems to have a consistent sequence for units but I am not sure what the guideline is. Do we have any statistics on how often the foot unit is first or second? Google comes up with many for either sequence. Perhaps it doesn't really matter. I don't mind either way.
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The sequence distance-force was common in the old metric "meter-kilograms" and "centimeter-kilograms", more common than "kilogram-meters", the order common for energy. (I have a torque wrench in "meter kilograms", for example.) Google can find several of them as
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Thanks for the great examples. Of course it was silly of me to assume imperial conventions come from SI. However, I stand by my assertion that lbf-ft predominates over ft-lbf for whatever reason and I suspect that's why SI adopted N-m. See googlefight:
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It's easy enough to see why that idea didn't catch on. The people who use the mass units would like to have both a spelled out word and a symbol for them, as would the people who use the force units (and, of course, those are often the same people).
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of 1 foot, or (what is the same thing, as regards turning) a couple of which the force is one poundal and the arm one foot. This we shall call a poundal-foot, thereby distinguishing it from the foot-poundal, which is the
British absolute unit of work.
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Theta is the angle between 'r' and 'F'; while the diagram on the page is correct in stating that the side in question is (F), that is not the correct quantity to use when determining torque. The REAL definition is above, and a proof is located in
652:
As I claimed above, the idea that we should distinguish the
English units of torque from the English units of energy and work far predates the International System of Units, which was only introduced in 1960. I have found a clear example:
563:
Both "pound-feet" (lbf¡ft) and "foot-pounds" (ft¡lbf) are in common use, as you discovered. Some experts and style guides recommend the former to distinguish the units of torque from the units of energy/work, a different quantity. See
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This is true for all cross products. The angle in question is ALWAYS the angle between the two vectors. The presence of a cosine term in the multiplication of two vectors implies a dot product, rather than a cross product.
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I think that if you looked into it carefully, you would find significant differences in usage in different fields of activities, geography, etc. More a matter of degree than of uniform usage in any particular
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BTW, Worthington, who named the "slug" as a unit of mass in an earlier (1904) edition of this book (which may well have contained much of the same information about torque), also had another bright idea:
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Sam said that torque is lbf¡ft, not ft¡lbf The sequence force¡distance is used almost without exception in metric units, so that is a parallel. I am aware not aware of any reason for the sequence. The
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I had been wondering about that, but I hadn't really cared enough to work it out until you mentioned it, mainly because I figured it would depend on exactly how the problem is phrased. The
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FYI, the 'Anon' making the edits has a BA in
Physics from the University of Maine, and I'm not too far behind; I'm currently finishing up my senior year in Physics at UMaine.
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and possibly link it (sparsely or at least initially) in articles? I'm somewhat new here and not sure that it's a valid use for redirects, but I think it would be useful. â
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consistency at all. On
Knowledge, ft¡lbf clearly predominates over lbf¡ft in this context, but that is probably still true but not so overwhelming outside Knowledge.
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You get confused too easily. Why is it okay to use the dot for scalar multiplication but not the cross? Wouldn't you instead get confused with the dot product?
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Futhermore, there are sources recommending pound-feet rather than foot-pounds going back to before SI ever existed. So your chronology was wrong there, too.
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1210:"Loosely speaking, torque is a measure of the turning force on an object such as a bolt" ... I love that quote. Torqur turns Loose bolts! Hahahahahha!
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by Grant Fowles and George
Cassiday, on pages 15-16. In order to use the angle theta as defined in the picture, the correct equation would have to be:
645:
Now let's deal with the silly notion that the order of terms in
English units should be determined by the order of terms in SI units. That's nonsense.
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First of all, the cosine term in the definition of torque listed on this page is NOT correct. Torque is a result of a vector cross product, that is:
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Well, there's a diagram. Not my best work, but if you think it might help clarify the formula, we can find a place in the article for it. â
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912:{\displaystyle {\boldsymbol {T}}=({\textrm {distance\ to\ centre}})\times \cos(\theta )\times {\textrm {force}}}
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http://www.googlefight.com/index.php?lang=en_GB&word1=%22lbf-ft%22+torque&word2=%22ft-lbf%22+torque
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version is correct as the problem is stated. Give me a few minutes here, and I'll have a better diagram. â
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on Knowledge. If you would like to participate, please visit the project page, where you can join
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on Knowledge. If you would like to participate, please visit the project page, where you can join
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Please help fix the broken anchors. You can remove this template after fixing the problems. |
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So we can probably add something along those lines in the first paragraph of that subsection.
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Can someone please verify that this is the correct formula for the magnitude of torque:
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London, New York, Bombay, Calcutta, and Madras: Longmans, Green, and Co., 1920., p. 9.
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Force applied at an angle; projection onto perpendicular is given by the cosine.
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Sorry, I didn't notice the second table on that page. Of course, they call it
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is used for both cross product and multiplication of two scalars, as in
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This article links to one or more target anchors that no longer exist.
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The definition of a cross product in scalar form is the following:
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Dynamics of Rotation: An Elementary Introduction of Rigid Dynamics,
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I've written this up under units. Thanks for the good questions!
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I thought that people here might have something to say about it.
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page. Do you think it would make sense to put a redirect in from
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I think the feet first is even more predominant when it comes to
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Nonetheless, there is no clear standard for English units today.
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is called \times in TeX, and someone took this too literally?
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Here's a little blurb to lay the sine/cosine issue to rest:
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Your link was bogus. Neither it nor anything else on the
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An anon keeps changing it to sin instead of cos... --
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Knowledge level-4 vital articles in Physical sciences
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673:Gravitation or Engineerâs British Unit of Torque.â
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1022:I find it very confusing that the same symbol
1271:Knowledge vital articles in Physical sciences
592:site says anything about the units of torque.
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1301:B-Class physics articles of High-importance
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618:âdo you take that as prescriptive as well?
520:] The anchor (Torque or moment of force)
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265:It is of interest to the following
23:for discussing improvements to the
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718:How can we writeup this factoid?
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1199:"Do as I torque, not as I talk!"
665:British Absolute Unit of Torque.â
447:Knowledge:WikiProject Engineering
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1247:09:10, 19 November 2023 (UTC)
1226:WT:MSM § Inline math notation
1202:"Do as I do, not as I say!".
441:and see a list of open tasks.
342:Knowledge:WikiProject Physics
336:and see a list of open tasks.
42:Put new text under old text.
1306:B-Class Engineering articles
345:Template:WikiProject Physics
923:17:05, July 18, 2005 (UTC)
50:New to Knowledge? Welcome!
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970:20:08, July 18, 2005 (UTC)
951:19:46, July 18, 2005 (UTC)
770:A question about redirects
473:project's importance scale
368:project's importance scale
1061:{\displaystyle a\times b}
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