ISO 31-3 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to mechanics.
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 after Isaac Newton |
| Moment of force, Torque |
M, |
|
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 alternate 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 after James Joule. The joule is dimensionally equivalent to the units of torque amd 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·m2/s3 |
Unit named after James Watt. |
| Pressure |
p |
pascal |
Pa |
1 Pa = 1 N / m2 = 1 kg/(m·s2) |
Named after Blaise Pascal. |
| Normal stress, Shear stress |
|
pascal |
Pa |
1 Pa = 1 N / m2 = 1 kg/(m·s2) |
Named after Blaise Pascal. |
| ... |
|
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