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Unit of Torque

  1. Aug 17, 2012 #1
    Why unit of torque is not m.N

    1.Torque=rFSinθ =>m.N
    2. 1 N.m = 1 Joule but 1 N.m in torque ≠ 1 Joule

    For the above 2 reasons i reckon it should have unit of m.N.
  2. jcsd
  3. Aug 17, 2012 #2


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    hi azizlwl! :smile:

    a newton-metre and a joule are the same thing

    but we tend to use one for torque and the other for energy, to avoid confusion :biggrin:

    see http://en.wikipedia.org/wiki/Joule#Confusion_with_newton_metre
    The use of newton-metres for torque and joules for energy is useful in helping avoid misunderstandings and miscommunications​

    (there are other units that describe more than one thing …

    for example, the pascal is a unit both of pressure and of energy density :wink:)
  4. Aug 17, 2012 #3


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    I read somewhere that we define the unit of torque as N m rather than m N, as the latter makes one want to say 'milli newton'.
  5. Aug 17, 2012 #4


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    A 'foot pound' was chosen, historically and arbitrarily, as the unit of work and a 'pound foot' was chosen as the unit of torque. When we went metric, the same convention regarding the order of force and distance was used. If it hadn't, then this forum would be cluttered with complaints about it - just like the whinges regarding the accepted direction of conventional electrical current.
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