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What are correct abbreviations for torque and energy in US Customary and S.I. systems? Both include distance and force. Do we write N-m and lbf-ft for both torque and energy? I always heard (years ago) torque expressed in "foot-pounds" of torque, meaning ft-lbf. I'm writing continuing education engineering courses and want to get terminology correct. Thanks

Qmechanic
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Bill
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  • Energy in customary units is a disaster because it is usually expressed in BTUs which is obviously not well suited for mechanical systems. I have never seen energy expressed in units of torque, and you should never do that. – John Alexiou Jan 30 '24 at 15:23

1 Answers1

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In SI the units for torque are Newton metres and the units for energy are Joules.

The two quantities have the same dimensions but not the same units. This has already been discussed several times. See for example Why is torque not measured in Joules?

I am fairly certain the US unit for torque is the foot pound as I know from experience this is used on US torque wrenches. I am not sure what the most commonly used unit for energy is, though some Googling suggests that the US may indeed use the foot pound for energy as well.

John Rennie
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  • NIST - Capitalization Unit Names: The names of all units start with a lowercase letter (meter, lumen, weber volt, etc.) except, of course, at the beginning of the sentence. There is one exception: in "degree Celsius" (unit symbol °C) the unit "degree" is lowercase but the modifier "Celsius" is capitalized. Thus, body temperature is written as 37 degrees Celsius. Unit Symbols: Unit symbols are written in lowercase letters (m for the unit "meter" or s for the unit "second"). Exceptions include the unit "liter" (L) and those units derived from the name of a person.. – Farcher Jan 30 '24 at 08:13
  • When the unit is derived from the name of a person, the symbol or the first letter of the symbol is an uppercase letter (W for the unit "watt" or Pa for the unit "pascal"). So newton metre (N m) and joule (J). – Farcher Jan 30 '24 at 08:15