My topic will clear concept of physical and non physical quantities

Physical and Non-Physical Quantities
Class 9 Physics Notes | Chapter: Physical Quantities and Measurement


1. Introduction
In Physics, we study matter, energy, motion, force, heat, light, electricity and many other natural phenomena.
For proper scientific study, we observe things and measure them. The terms used in science can be divided
into physical quantities and non-physical quantities.

2. Physical Quantities
Definition: A physical quantity is any quantity that can be measured and expressed with a numerical value
and a unit.

General form: Physical Quantity = Numerical Value + Unit
Example: If the length of a table is 2 metres, then 2 is the numerical value and metre (m) is the unit.

Important Examples of Physical Quantities
Physical Quantity Symbol SI Unit Example

Length l metre (m) Height of a door = 2 m

Mass m kilogram (kg) Mass of a bag = 5 kg

Time t second (s) Time taken = 10 s

Temperature T kelvin (K) Temperature = 300 K

Electric current I ampere (A) Current = 2 A

Area A square metre (m²) Area of room = 20 m²

Volume V cubic metre (m³) Volume of box = 1 m³

Speed v metre per second (m/s) Speed = 15 m/s

Force F newton (N) Force = 10 N



Characteristics of Physical Quantities
• They can be measured by an instrument.
• They have a numerical value.
• They are expressed with a proper unit.
• They can be compared mathematically.
• They are used in scientific laws and calculations.

Types of Physical Quantities
A. Base Quantities
Base quantities are independent physical quantities. They are not derived from other quantities. The SI system
has seven base quantities.

Base Quantity SI Unit Symbol

Length metre m



Class 9 Physics Notes - Physical and Non-Physical Quantities Page 1