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ISO 31-3 is the part ofinternational standardISO 31 that defines names and symbols forquantities andunits related tomechanics. It was published on 27 August 1992 and withdrawn on 17 March 2006 due to being superseded byISO 80000-4.^[1]

Its definitions include (note boldfaced symbols mean quantity is a vector):

Quantity		Unit			Remarks
Name	Symbol	Name	Symbol	Definition
Force	F	newton	N	1 N = 1 kg·m/s2	Unit named afterIsaac Newton
Moment of force,Torque	M,${\displaystyle \mathit{\tau }}$		N·m	1 N·m = 1 kg·m2/s2	The unit is dimensionally equivalent to the units of energy, the joule; but the joule should not be used as an alternative for the newton metre.
Linear momentum	p		kg·m/s or N·s
(Linear) impulse	J		N·s or kg·m/s
Angular momentum	L		kg·m2/s or N·m·s
Mechanical energy,Work	E,W	joule	J	1 J = 1 kg·m2/s2 = 1 Pa·m3 = 1 W·s	Unit named afterJames Joule. The joule is dimensionally equivalent to the units oftorque andmoment of force but should be used in preference to the newton metre (N·m).
Power	P	watt	W	1 W = 1 J/s = 1 N·m/s = 1 kg·m2/s3	Unit named afterJames Watt.
Pressure	p	pascal	Pa	1 Pa = 1 N / m2 = 1 kg/(m·s2)	Named afterBlaise Pascal.
Normal stress, Shear stress	${\displaystyle \sigma ,\tau }$	pascal	Pa	1 Pa = 1 N / m2 = 1 kg/(m·s2)	Named afterBlaise Pascal.
...

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