The ammount of matter contained in a body is can be termed as mass.
According to different system of unit are used in the different parts of the world. These systems are mainly the methods of defining the three fundamental units. The most widely used system of units is CGS or French or metric system.
In 1960, at Eleventh General Conference on Weights and Measures held at Paris, an international system of units is adopted to have a consitent system of units and also to simplify the communications amon the scientists. This system of units is known as Le Systeme International d' Unites abbreviated as SI units.
- C.G.S. or French or Metric System: This system was originated in France but now it is used in the scientific measurements and also is widely used throughout the world. In this system, the unit of length is centimetre, the unit of mass in gram and the units of time is second. From the initial letters of the words centimetre, gram and second this system is called the C.G.S. system.
- S.I. units: In this system in addition to units of length, mass and time, units of electric current, temperature, luminous intensity and quantity of substance i.e., seven basic units in all are adopted. These are-
PHYSICAL QUANTITY UNIT SYMBOL
1. length metre m
2. mass kilogram kg
3. time second s
4. electric current ampere A
5. temperature kelvin K
6. luminious intensity candela cd
7. quantity of a substance mole mol
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