Newton-metre - Wikipedia

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Appearance move to sidebar hide From Wikipedia, the free encyclopedia SI unit of torque For the instrument that measures forces in newtons, see Spring scale.

newton-metre
A force of one newton applied perpendicularly to the end of a moment arm that is one metre long results in one newton-metre of torque.
General information
Unit system	SI
Unit of	torque
Symbol	N⋅m, N m
Conversions
1 N⋅m in ...	... is equal to ...
FPS system	0.73756215 lbf.ft
inch⋅pound-force	8.8507 in lbf
inch⋅ounce-force	141.6 in oz

The newton-metre (also non-hyphenated, newton metre; symbol N⋅m[1] or N m[1])[a] is the unit of torque (also called moment) in the International System of Units (SI). One newton-metre is equal to the torque resulting from a force of one newton applied perpendicularly to the end of a moment arm that is one metre long.

The unit is also used less commonly as a unit of work, or energy, in which case it is equivalent to the more common and standard SI unit of energy, the joule.[2] In this usage the metre term represents the distance travelled or displacement in the direction of the force, and not the perpendicular distance from a fulcrum (i.e. the lever arm length) as it does when used to express torque. This usage is generally discouraged,[3] since it can lead to confusion as to whether a given quantity expressed in newton-metres is a torque or a quantity of energy.[4] "Even though torque has the same dimension as energy (SI unit joule), the joule is never used for expressing torque".[4]

Newton-metres and joules are dimensionally equivalent in the sense that they have the same expression in SI base units,

1 N ⋅ m = 1 kg ⋅ m 2 s 2 , 1 J = 1 k g ⋅ m 2 s 2 {\displaystyle 1\,{\text{N}}{\cdot }\mathrm {m} =1\,{\frac {{\text{kg}}{\cdot }{\text{m}}^{2}}{{\text{s}}^{2}}}\quad ,\quad 1\,\mathrm {J} =1\,{\frac {\mathrm {kg} {\cdot }\mathrm {m} ^{2}}{\mathrm {s} ^{2}}}}

but are distinguished in terms of applicable kind of quantity, to avoid misunderstandings when a torque is mistaken for an energy or vice versa. Similar examples of dimensionally equivalent units include Pa versus J/m3, Bq versus Hz, and ohm versus ohm per square.

Conversion factors

[edit]

• 1 kilogram-force-metre = 9.80665 N⋅m[5][6]
• 1 newton-metre ≈ 0.73756215 pound-force-feet
• 1 pound-foot ≡ 1 pound-force-foot ≈ 1.35581795 N⋅m
• 1 ounce-inch ≡ 1 ounce-force-inch ≈ 7.06155181 mN⋅m (millinewton-metres)
• 1 dyne-centimetre = 10−7 N⋅m

See also

[edit]

• Bending moment
• Spring scale
• Torque tester
• Newton-second, the SI unit of impulse

Notes

[edit]

1. ^ The nonstandard notation "Nm" occurs in some fields.

References

[edit]

1. ^ a b "BIPM – unit symbols". Archived from the original on 2017-10-01. Retrieved 2016-10-18.
2. ^ For example: Eshbach's handbook of engineering fundamentals – 10.4 Engineering Thermodynamics and Heat Transfer "In SI units the basic unit of energy is newton-metre".
3. ^ Halliday Resnick Walker, Fundamentals of Physics (9th ed.), p. 309, The SI unit of torque is the newton-meter. In our discussion of energy we called this combination the joule. But torque is not work and torque should be expressed in newton-meters, not joules
4. ^ a b "BIPM – special names". Archived from the original on 2019-03-21. Retrieved 2015-09-27.
5. ^ "Mechanical Engineering Formulas Pocket Guide". p. 6.
6. ^ Donald V. Rosato; Marlene G. Rosato; Dominick V. Rosato. "Concise encyclopedia of plastics". p. 621.

v t e SI units
Base units	ampere candela kelvin kilogram metre mole second
Derived units with special names	becquerel coulomb degree Celsius farad gray henry hertz joule katal lumen lux newton ohm pascal radian siemens sievert steradian tesla volt watt weber
Other accepted units	astronomical unit dalton day decibel degree of arc electronvolt hectare hour litre minute minute and second of arc neper tonne
See also	Conversion of units Metric prefixes Historical definitions of the SI base units 2019 revision of the SI System of units of measurement
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