Unit of Torque

  • Thread starter azizlwl
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  • #1
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Main Question or Discussion Point

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.
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
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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:)
 
  • #3
CAF123
Gold Member
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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'.
 
  • #4
sophiecentaur
Science Advisor
Gold Member
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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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