Systems of Units Physics Notes

Systems of Units:
To measure the fundamental physical quantities length, mass and time, we have three systems of units. They are:

C.G.S. System
M.K.S. System
F.P.S. System (British system)

In all these three systems only three physical quantities mass, length and time are considered to be the fundamental quantities.
1. C.G.S. System: This system of units was set up in France and it is based on centimeter,, gram and second as the three basic units for length, mass and time respectively.

2. M.K.S. System: This system is based on metre, kilogram and second as the fundamental units of length, mass and time respectively. It is also a metric system of units and closely related to the C.G.S. system of units.

3. F.P.S. System: This system of units, also known as the British system of units, is based on foot, pound and second as the fundamental units of length, mass and time. Its use in scientific work is declining more and more.

Merits of S.I. system:
The merits of the international system of units are:

This system makes use of only one unit for one physical quantity. Therefore, it is a rational system.
S.I is a coherent system of units i.e., a system based on a certain set of fundamental units, from which all derived units are obtained by multiplication or division without introducing the numerical factors.
It is a metric system i.e., the multiple and submultiple of units are expressed as a power of 10.
It is an internationally accepted system of units.
S.I. has a broader base. It has seven base units and two supplementary units.