Measurements [Physics]

Physical quantities

those quantities which can be measured accurately are called physical quantities

The fundation of physics rest upon physical quantities

for exemple mass length thime velocity force density temperature electricalcurrent etc

Base Quantities:

these are the minimum number of those quantities in term of which other quantities can be defined

Derived Quantities 

those quantities whos definations are based on other physical quantities called as derived quantities
"the measurement of a base quantities"

involves following two steps:

1) the choice of standered 

2)estblishment of a procedure for comparing the quantity to be measured with the standerd 

An Ideal Standerd has two characteristics

a) It is accessible,

b) it is invariable.

international system of unit

In 1960, an international committee agreed on a set of definations and standered to descirbe the physical quantities this system is called the system internation [SI]
this system is based up on 

a)Base quantities

b)supplimenteary unit 

c)derived unit

A) base unit:-

the unit defined arbitrarily for the measurement of seven base quantities in comparison with them are called base quantities

the name of base quantiirs and symbols are given below:

sr.no           physical quantitites      Si unit         symbols

1                      length                       meter             m

2                      mass                          kilogram       kg

3                      time                           second           s

4                       electrical current    ampere         a

5                       Temperature           kelvin            k

6                       light intancity         candela         cd

7                       amount of substance          mole              mol