Physics is a study of basic laws of nature and their manifestation in different phenomenas.
Principal thrusts in Physics
• There are two principal thrusts in Physics; • 1.Unification 2. reduction
Unification
• Efforts are made to explain different phenomena in nature on the basis of one or minimum laws. This is principle of Unification.
Example: Phenomena of apple falling to ground, moon revolving around earth and weightlessness in the rocket, all these phenomena are explained with help of one Law that is, Newtons Law of Gravitation.
Reductionism
• To understand or to derive the properties of a bigger or more complex system the properties of its simpler constituents are taken into account. This approach is called reductionism.
It is supposed to be the heart of Physics.
For example a complex thermo dynamical system can be understood by the properties of its constituent like kinetic energy of molecules and atoms.
• The scope of Physics can be divided in to two domains; Macroscopic and Microscopic.
• Macroscopic domain includes phenomena at the level of Laboratory, terrestrial and astronomical scales.
• Microscopic domain I ncludes atomic, molecular and nuclear phenomena.
• Recently third domain in between is also thought of with name Mesoscopic Physics. This deals with
group of Hundreds of atoms
• Scope of physics is very wide and exciting because it deals with objects of size as large as Universe
(1025m) and as small as 10-14 m, the size of a nucleus.
The excitement of Physics is experienced in many fields Like:
• Live transmissions through television.
• Computers with high speed and memory,
• Use of Robots,
• Lasers and their applications
Physics in relation to other branches of Science
Physics in relation to Chemistry:
• Chemical bonding, atomic number and complex structure can be explained by physics phenomena
of Electrostatic forces,
• taking help of X-ray diffraction.
Physics in relation to other Science
• Physics in relation to Biological Sciences: Physics helps in study of Biology through its inventions.
Optical microscope helps to study bio-samples, electron microscope helps to study biological cells. X-rays have many applications in biological sciences. Radio isotopes are used in cancer.
Physics in relation with Astronomy:
• Giant astronomical telescope developed in physics are used for observing planets. Radio telescopes
have enabled astronomers to observe distant limits of universe.
• Physics related to other sciences: Laws of Physics are used to study different phenomenas in other
sciences like Biophysics, oceanography, seismology etc.
Fundamental Forces in Nature
There is a large number of forces experienced or applied. These may be macroscopic forces like gravitation, friction, contact forces and microscopic forces like electromagnetic and inter-atomic forces. But all these forces arise from some basic forces called Fundamental Forces.
Fundamental Forces in Nature:
1. Gravitational force.
• It is due to Mass of the two bodies.
• It is always attractive.
• It operates in all objects of universe.
• Its range is infinite
It’s a weak force. 10-38 times compared to strong Nuclear force
2.Electromagnetic Forces:
• It’s due to stationery or moving Electrical charge
• It may be attractive or repulsive.
• It operates on charged particles
• Its range is infinite
• Its stronger 1036 times than gravitational force but 10-2 times of strong Nuclear force.
3. Strong nuclear force:
• Operate between Nucleons
• It may be attractive or repulsive
• Its range is very short, within nuclear size
• Its strongest force in nature
4.Weak Nuclear force:
(10-15 m).
• Operate within nucleons I.e. elementary particles like electron and neutrino.
• It appears during radioactive b decay.
• Has very short range 10-15m.
• 10-13 times than Strong nuclear force.
Conservation Laws
• In any physical phenomenon governed by different forces, several quantities do not change with time. These special quantities are conserved quantities of nature.
1. For motion under conservative force, the total mechanical Energy of a body is constant.
2. Total energy of a system is conserved, and it is valid across all domains of nature from microscopic to macroscopic. Total energy of the universe is believed to be constant.
3. Conservation of Mass was considered another conservation law, till advent of Einstein. Then it was converted to law of conservation of mass plus energy. Because mass is converted into energy and vice-versa according to equation E = mc2 The examples are annihilation and pair production.
4. Momentum is another quantity which is preserved. Similar is angular momentum of an isolated system. 5. Conservation of Electric charge is a fundamental law of nature.
6. Later there was development of law of conservation of attributes called baryon number, lepton number and so on.
The laws of nature do not change with change of space and time. This is known as symmetry of space and time. This and some other symmetries play a central role in modern physics. Conservation laws are connected to this.
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