ISO 31-3 explained

ISO 31-3 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to mechanics. It is superseded by ISO 80000-4.

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/s^2	Unit named after Isaac Newton
Moment of force, Torque	M, \boldsymbol{\tau}		N·m	1 N·m = 1 kg·m^2/s^2	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·m^2/s or N·m·s
Mechanical energy, Work	E, W	joule	J	1 J = 1 kg·m^2/s^2 = 1 Pa·m^3 = 1 W·s	Unit named after James Joule. The joule is dimensionally equivalent to the units of torque and moment 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·m^2/s^3	Unit named after James Watt.
Pressure	p	pascal	Pa	1 Pa = 1 N / m^2 = 1 kg/(m·s^2)	Named after Blaise Pascal.
Normal stress, Shear stress	\sigma, \tau	pascal	Pa	1 Pa = 1 N / m^2 = 1 kg/(m·s^2)	Named after Blaise Pascal.
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