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Give a note on Classical Physics.

Classical Physics deals mainly with macroscopic phenomena and includes subjects like Mechanics, Electrodynamics, Optics and Thermodynamics.


What is mechanics?

Mechanics founded on Newton’s Laws of Motion and the Law of Gravitation deals with the motion (or equilibrium) of particles, rigid and deformable bodies and general systems of particles.


State some problems of mechanics.

The propulsion of a rocket by a jet of ejecting gases, propagation of water waves or sound waves in air, the equilibrium of a bent rod under a load, etc., are problems of mechanics.


Define Electrodynamics.

Electrodynamics deals with electric and magnetic phenomena associated with charged and magnetic bodies.


Does imagination play any role in Physics?

Yes, imagination has played its role in the development of Physics. Huygen’s principle, Maxwell’s equation, Schrodinger principle, Bohr’s theory, Pauli’s exclusion principle, etc. were the imaginations of scientists which have been successfully employed to explain the various phenomena occurring in Nature.


What contributions has Physics made in the development of biological sciences?

Physics has made the following contributions in the development of biological sciences:

(i) Electron microscope, which we can observe the structure of a cell.

(ii) X-ray and neutron diffraction techniques for studying the structure of a cell.

(iii) Radio-isotopes for radiation treatment of cancer and other diseases.


Discoveries and developments in Physics have a direct impact on the society or mankind. Explain.

Whatever is discovered in Physics immediately becomes useful to society in some form or the other. For example, developments in the field of communication such as telephone, telegraph, tele printer, telex, etc. enable us to quickly exchange messages between far off places. The development of the radio and television have made instant communication possible over inaccessible distances. Now the use of artificial satellites has made it possible for us to instantly see any event in any part of the world. Recent technological developments like microelectronics, lasers, computers, super conductivity, nuclear fusion, etc. have entirely changed the thinking and living of mankind or society.


Name two advantages made in technology on the basis of physics.

The following two advantages mentioned show the advantages made in technology on the basis of physics

(i) The study of satellites has made it possible to force cast the weather very accurately.

(ii) Due to the discovery of nuclear fission, a large amount of energy becomes available in nuclear power stations due to conversion of mass into energy.


Explain the law of conservation of mass-energy with an example.

According to Einstein, mass and energy are inter-convertible quantities. That is, mass of a system can be converted into energy and the energy of a system can be converted into mass. But the sum of mass and energy of a system remains constant.

The energy (E) equivalent to mass (m) is given by the relation

E = mc2

Where c = 3 ×108 ms-1 is the speed of light in air or vacuum.

When 1g of coal is completely burnt, then energy produced is given by

E = mc2
  = (1g) ×(3 ×108 ms-1)2
  = 10-3Kg×9 ×1016 ms-2
  = 9
×1013 joule.


Give two examples for gravitational force.

The two examples for gravitational force are as follows:

(i) The weight of a body is the force with which the Earth attracts it towards the centre.

(ii) The force of attraction between various bodies in the Universe.


Every walk of life is effected by the technological application of physics. Justify this point of view.

The following points help to justify the fact that every walk of life is affected by the technological application of physics.

(i) Development of telephone, telegraph, tele printers etc, has made communication of message quite rapid.

(ii) Conversion of heat energy into mechanical work has made it convenient to develop the steam engine with very high efficiency.

(iii) Development of new devices and technological advancements has made scientific measurements more accurate and more precise.


What are the characteristics of nuclear force?

The characteristics of nuclear forces are as follows:

(i) It is attractive in nature.

(ii) It acts over a very short distance (10-15m) i.e. it is a short range force.

(iii) It is 100 times stronger than electromagnetic force and 1038 times stronger than gravitational force.

(iv) It is a non-central force i.e., it does not act along the line joining the centers of two particles.

(v) It does not obey the inverse square law.


Give some examples in physics which are exciting and educative.

Following are some examples in Physics that are exciting and educative:

(i) The fall of an apple leads us to understand gravitation.

(ii) The heat energy of steam runs an engine.

(iii) A spherical liquid drop helps us to understand surface tension.


Comment on the statement: "The most incomprehensible thing about the world is that it is comprehensible."

The world around us is very complex because of the occurrence of millions of phenomena. Moreover, we come across wide ranges of mass, length and time. But these can be understood in terms of few basic laws. In other words, the complex nature of the physical world can be understood in terms of few basic laws. This is a very exciting state of affair. Einstein expressed this excitement by saying that the most incomprehensible thing about the world is that it is comprehensible.


Give the dissimilarities between electrostatic force and gravitational force.

The following are the dissimilarities between electrostatic force and gravitational force

(i) While the gravitational forces are always attractive in nature, the electrostatic forces may be attractive or repulsive.

(ii) While the gravitational constant or proportionality depends upon the medium, the electrical constant of proportionality definitely depends upon the medium.

(iii) Electrostatic forces are extremely large as compared to gravitational forces.


What is the main aim of science?

The main aim of science is to find the truth behind the various phenomena taking place in the universe.


State law of conservation of linear momentum.

The law of conservation of linear momentum states that if no external force acts on a system, the linear momentum of the system remains constant.


State the law of conservation of angular momentum.

The law of conservation of linear momentum states that if no external torque acts on a system then the total angular momentum of the system always remains constant.


State the law of conservation of energy.

The law of conservation of energy states that energy can neither be created nor destroyed. However,  it may change from one form to another.


Why do we call Physics an exact Science?

Physics is called an exact Science because it is based on measurement of fundamental quantities.


Define the basic aim of science.

The basic aim of science is to search for the truth. It tries to analyse the natural phenomena taking place around us.


Name the scientist and the country of his origin whose field of work was 'Cosmic Rays'.

Mr. Hess, Austria.


Why was science called natural philosophy in earlier days?

Science was called as natural philosophy because in earlier days, scientific knowledge was gained from direct study of natural phenomena.


What do you understand by scientific attitude?

The attitude of solving problems by adopting scientific method is called as scientific attitude.


The fate of society is linked with the development of physics, Explain.

The development of physics has changed our life. This has become possible due to inventions like electricity, radio, television, rockets, computers, X-rays, nuclear medicine, nuclear reactors etc. On one hand where physics has made our life comfortable, it has also developed the nuclear weapons which can destroy the whole living world within time. Hence we conclude that the fate of society is linked with the development of physics.


Name some key scientific and technological advances, which led to first industrial revolution in England and Europe.

Some of the key scientific and industrial advances, which led to industrial revolution in 1750 A.D., were

(i) steam

(ii) blast furnace

(iii) power loom etc.

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