Classification of Physical Quantities - Sept 25th 2024

Measurement of a physical quantity

Consider a constant quantity as a standard and then find the number that expresses how many times the standard quantity is contained in the given physical quantity.

The standard quantity is called a unit
Physical quantity = numerical value x unit

All physical quantities are classified into two types
They are:

1. Fundamental or Base Quantities and Units
In physics 7 quantities are taken as fundamental quantities and the first 5 of them are considered as base quantities.

They are listed with their SI in the table below.
SI [ System International ]

2. Derived Quantities and Units
All other quantities, called derived quantities are obtained from one or more of the base quantities.

These units are obtained from the base units by multiplication or division. Some examples are given below.

p = rho

The unit of some derived quantit2ies would be rather complicated if written in terms of the base unit.

These are named after the famous scientist. Some of them are listed below. Note that the unit symbols all have Capital letters in these cases.