SI Base units
Fundamental units of
physics
From these seven
fundamental units, all other derived units can be formulated. For
instance, velocity is metres per second and force is kilogram-metres per second.
(note: the SI spelling of metre)
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|
SI Base Units |
|
Base Quantity |
Base Unit |
Based on |
Symbol |
|
Length |
metre |
distance light travels in 1/299792458 seconds |
m |
|
Mass |
kilogram |
mass of platinum-iridium cylinder stored in Sèrves,
France |
kg |
|
Time |
second |
9,192,631,770 vibrations of a certain wavelength of
light from cesium-133 |
s |
|
Temperature |
Kelvin |
Scale using Celsius degrees but starting from absolute
zero |
K |
|
Amount of Substance |
mole |
Avogadro’s Number (6.022×1023) of atoms or
molecules of the substance |
mol |
|
Electric Current |
Ampere |
the charge on 6.25×1018 electrons flowing
past a point in one second |
A |
|
Luminous Intensity |
candela |
amount of light emitted through 1/60 cm2 from
molten platinum at its melting point |
cd |
|
|