Introduction To Fundamental Quantities And Units | Physics
No physical quantity is meaningful unless it can be exactly measured, quantified and given a unit. In other words, we need two thing specify a physical quantity,the number of quantity and its unit of measurement.
There are three important fundamental quantities in physics. These are lenth, mass and time. The units of these quantities form the base units upon which the units of other quantities depend. Other fundamental quantities are electric current, temperature, amount of substance and luminous intensity.
Scientists all over the world try to use the same units to measure the same quantity. For example, the British and others prefer to use inches to measure the same quantity for example, the British and others prefer to use inches to measure length and pounds to measure weight.
In most scientific measurements, the system of units now accepted internationally is called international system of units, often called SI unit. The fundamental units are shown in the table below.
If you consider only the first three fundamental quantities and units, i.e length (metres), mass (kilograms), time (second) the SI units can be referred to as MKS (metre-kilogram-seconds) system.
Another sub system of MKS is the cgs system in which the standard units of length, mass and time are centimetre, gram and second respectively.
The SI units are the principal system of units used in scientific work today.
SI Fundamental quantities and units:
