Chapter-1 Physical quantities and measurement 9th Class Physics Notes

 Define Science?

"Science is the knowledge gained through observation and experience. "The word science is derived from the Latin word Scientia, which means knowledge.

Science Technology and Society:

Man has always been fascinated by the wonders of nature and has been in search of truth and reality. He looks at different phenomena and tries to find their answers through logical reasoning.
Not until the eighteenth century, but under the same subject called natural philosophy, various aspects of material things were studied. But as knowledge grew, it split into two main streams:

Physical Sciences

It deals with the study of inanimate objects.


It deal the study of living things like animals and plants.


Measurement is not limited to science, they are part of our lives. They play an important role in describing and understanding the physical world. Over the centuries, man has improved the methods of measurement.

What is Physics?

"Physics is a branch of science that deals with matter, energy and their relationships."

Physics is divided into the following branches.


It is the study of the movement of objects, their causes and effects.


It deals with the nature of heat, the methods of transfer and the effects of heat.


It deals with the physical aspects of sound waves, their output, features and applications.


It is the study of the physical aspects of light, its function in its properties and the use of optical instruments.


It is a study of charges in relaxation and motion, their effects and relationship to magnetism.

Atomic Physics

It is a study of the structure and properties of atoms.

Nuclear Physics

It has to do with the properties and behavior of the nucleus and the particles inside the nucleus.

Plasma Physics

It is a study of the productive, properties of the ionic state of the fourth state of matter.

Geo Physics

This is the study of the internal structure of the earth.

Write the Types of Physical Science

In the nineteenth century, the physical sciences were divided into five separate disciplines: 1. Physics 2. Chemistry 3. Astronomy 4. Geology 5. Meteorology
The most basic of these is physics. The laws and principles of physics help us to understand nature.

The Importance of Physics

Rapid advances in science in recent years have been made possible by discoveries and inventions in the field of physics. Technologies are the application of scientific principles. Most of the technologies in our modern society around the world are related to physics .For example Means of transportation such as cars and aero planes are built on the principles of mechanics.
Electricity is used not only to generate light and heat but also mechanical energy which is obtained from fans and electric motors. Home appliances such as air conditioners, vacuum cleaners, washing machines and microwave ovens are the result of the hard work of physicists in the field of physics.

Write Physicals Quantities and their Types

"All measurements are called physical quantities. "For e.g. length, mass, time and temperature, etc. 


Base Quantities

"Basic quantities are quantities on the basis of which other quantities are expressed."

There are seven physical quantities that form the basis of other physical quantities. These physical quantities are called basic quantities. These are length, mass, time, electric current, temperature, light intensity, and the amount of matter.

Derived Quantities 

"The amount that is expressed in terms of the basic quantity is derived from the quantity. "The physical quantity expressed in terms of the basic quantity is called the derived quantity. These include area, volume, speed, power, work, energy, power, electric charge, electrical capacity, and so on.


"Once a standard is set for a quantity, then that standard can be expressed in terms of the quantity. This standard quantity is called a unit.


"A word or letter that is added before a unit and stands for multiplication or subtraction of that unit is called a prefix." Some quantities are either too large or too small, e.g. 250,000 Mand 0.000,002G etc. SI units have the advantage that their regulations and sub-regulations can be used in the same way as before. These prefixes are useful for expressing large or small quantities.
Divided 3000 by 100 and write 3 x 10 3.

Scientific Notation

"In the scientific symbol, a number is represented as some power of ten, the number of which is between 1 and 10."
The moon is 384 billion meters away from the earth. The distance of the moon from the earth can also be expressed as 3.84 x108 m. This form of expression of a number is called standard form or scientific indicator.

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