SI Units
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The SI Unit system (from the French: Système international d'unités, "international system of units") forms the basis of standard measurements both within the sciences and the wider world. Each of the major physical quantities has a SI unit associated with its use; others, known as derived quantities, have their units formed from combinations of these base units, related to the formulae used to derive them.
Base UnitsEdit
There are seven quantities which have base units associated with them; these form the basis for every other SI unit in existence.
Quantity | SI Unit | Unit Symbol | Quantity Symbol |
---|---|---|---|
Length | meter | m | l |
Mass | kilogram | kg | m |
Time | second | s | t |
Electric Current | ampere | A | I |
Temperature | kelvin | K | T |
Amount of Substance | mole | mol | n |
Luminous Intensity | candela | cd |
Derived UnitsEdit
These units are SI units which may be derived from the equation(s) used in the calculation of the quantities associated with them. They are usually given separate names and symbols in order to make their use easier.
Quantity | Base Units | SI Unit | Unit Symbol | Quantity Symbol |
---|---|---|---|---|
Area | m^{2} | Metres Squared | m^{2} | A |
Volume | m^{3} | Metres Cubed | m^{3} | V |
Density | kg m^{-3} | Kilograms per Metre Cubed | kg m^{-3} | ρ |
Velocity | m s^{-1} | Metres per Second | m s^{-1} | v |
Acceleration | m s^{-2} | Metres per Second Squared | m s^{-2} | a |
Momentum | kg m s^{-1} | Kilogram Metre per Second | kg m s^{-1} | p |
Moment of Inertia | kg m^{2} | Kilogram Metre Squared | kg m^{2} | I, J |
Angular Momentum | kg m^{2} s^{-1} | Kilogram Metre Squared per Second | kg m^{2} s^{-1} | L |
Force | kg m s^{-2} | Newton | N | F |
Energy or Work | kg m^{2} s^{-2} | Joule | J | E, W |
Power | kg m^{2} s^{-3} | Watt | W | P |
Pressure or Stress | kg m^{-1} | Pascal | Pa | p |
Surface Tension | kg s^{-2} | Newton per Metre | N m^{-1} | γ |
Viscosity | kg m^{-1} s^{-1} | Kilogram per Metre per Second | kg m^{-1} s^{-1} | η |
Frequency | s^{-1} | Hertz | Hz | ν, f |