Units and Measurement

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Mass is a basic property of matter. It does not depend on the temperature, pressure or location of the object in space. The SI unit of mass is kilogram (kg).

There is an important standard unit of mass, called the unified atomic mass unit (u), which has been established for expressing the mass of atoms as 1 unified atomic mass unit = 1u
= (1/12) of the mass of an atom of carbon-12 isotope ${}_6{}^{12}C$ including the mass of electrons
= 1.66 10^-27 kg

Masses of the objects, we come across in the universe, vary over a very wide range. These may vary from a tiny mass of the order of 10^-30 kg of an electron to the huge mass of about 10⁵⁵ kg of the known universe.