Study Notes: Physical Quantities and Measurement

Physical Quantities and Measurements full chapter Study notes for the students of 9th Class. Feel free here, Learn these questions, and improve your grades in Physics.

1. Define Science.

The knowledge gained through observations and experimentations is called Science. The word Science id derived from the Latin word scientist, which means knowledge. Not until the eighteenth century, various aspects of material objects were studied under a single subject called natural philosophy.

2. Describe the division of science into who main streams.

Ans: Division of Science: As the knowledge increased it was divided into two main streams.

  • Physical Science: It deals with the study of non-living things.
  • Biological Science: It deals with the study of living things.

3. Define Physics.

Ans: Physics is that branch of science which deals with the study of properties of matter-energy and their mutual relationship.

4. Describe the different branches of physics.

Ans: Branches of physics are

  1. Mechanics: It deals with the motion of objects, their causes, and effects
  2. Heat: It deals with the nature of heat modes of transfer and the effects of heat.
  3. Sound: It deals with the physical aspects of sound waves, their production, properties, and applications.
  4. Light (Optics): It is the study of the physical aspects of light, its properties, working, and use of theoretical instruments.
  5. Electricity and Magnetism: It deals with the study of the charges at rest and in motion, their effects, and their relationships with magnetism.
  6. Atomic Physics: At is the study of the structure and properties of atoms.
  7. Nuclear Physics: It deals with the properties and behavior of nuclei and the particles within the nuclei.
  8. Plasma Physics: It deals with the study of production, properties of the ionic state of matter - the fourth state of matter.
  9. Geophysics: This branch of physics deals with the study of the internal structure of the earth.

5. Describe the Lord Kelvin statement?

Kelvin Statement:

When you can measure what you are speaking about and express it in numbers, you know something about it. When you can not measure what you are speaking about or you can not express it in number, your knowledge is of a meager and of an unsatisfactory kind.

6. Describe the crucial role of physics in science, technology and society?

Ans: Crucial role of physics in science, technology, and society:

The rapid progress in science during recent years has become possible due to the discoveries and inventions in the field of Physics. The technologies are the applications of scientific principles. Most of the technologies of our modern society throughout the world are related to Physics.


1. A car is made on the principles of mechanics and refrigerators are based on the principles of thermodynamics.

2. Consider pulleys that make it easy to lift heavy loads.

3. Electricity is used not only to get light and heat but also to mechanical energy that drives fans and electric motors etc.

4. Consider the means of transportation such as cars and airplanes, domestic appliances such as air-conditioners, refrigerators, vacuum cleaners, washing machines, and microwave ovens, etc.

5. Similarly, the means of communication such as radio, TV, telephone, and computer are the result of applications of Physics. The devices have made out lives much easier, faster, and more comfortable than the past.

6. A mobile phone allows us to contact people anywhere in the world and to get latest worldwide information. We can take and save pictures, send and receive messages from our friends. We can also receive radio transmission and can use it as a calculator as well.

7. List the harmful effects of the scientific inventions on nature.

Ans: The scientific inventions have also caused harm and destruction of serious nature. One of which is environmental pollution and the other is deadly weapons.

8. Explain with examples that science is based on physical quantities which consist of numerical