Physical World and Measurement (CHAPTER-Ⅰ)

 PHYSICAL WORLD 

WHAT IS PHYSICS ?

👉Physics is the science of how things work.

👉Physics is the natural science that studies matter, its motion and behavior through space and time, and the related entities of energy and force. Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe.

👉 Physics is a basic discipline in the category of Natural Sciences, which also includes other disciplines like Chemistry and Biology. The word Physics comes from a Greek word meaning nature. Its Sanskrit equivalent  is Bhautiki that is used to refer to the study of the physical world. A precise definition of this discipline is neither possible nor necessary. We can broadly describe physics as a study of the basic laws of nature and their manifestation in different natural phenomena. The scope of physics is described briefly in the next section. Here we remark on two principal thrusts in physics : unification and reduction.

In Physics, we attempt to explain diverse physical phenomena in terms of a few concepts and laws. The effort is to see the physical world as manifestation of some universal laws in different domains and conditions. For example, the same law of gravitation (given by Newton) describes the fall of an apple to the ground, the motion of the moon around the earth and the motion of planets around the sun. Similarly, the basic laws of electromagnetism (Maxwell’s equations) govern all electric and magnetic phenomena.

In Simple Word🤷‍♂️

Physics is the study of energy and matter in space and time and how they are related to each other. Physicists assume the existence of mass, length, time and electric current and then define (give the meaning of) all other physical quantities in terms of these basic units.

What is Science and what is the Scientific Method?

Science is a systematic attempt to understand natural phenomena in as much detail and depth as possible, and use the knowledge so gained to predict, modify and control phenomena. Science is exploring, experimenting and predicting from what we see around us. The curiosity to learn about the world, unravelling the secrets of nature is the first step towards the discovery of science.

The scientific method involves several interconnected steps : Systematic observations, controlled experiments, qualitative and quantitative reasoning, mathematical modelling, prediction and verification or falsification of theories.

SCOPE AND EXCITEMENT OF PHYSICS

Basically, there are two domains of interest : 

1. Macroscopic

2. Microscopic

1. Macroscopic

The macroscopic domain includes phenomena at the laboratory, terrestrial and astronomical scales. Classical Physics deals mainly with macroscopic phenomena and includes subjects like Mechanics, Electrodynamics, Optics and Thermodynamics.

2. Microscopic

The microscopic domain includes atomic, molecular and nuclear phenomena. Quantum Physics deals mainly with microscopic phenomena and includes subject like Atom, Nuclear physic, Nature of electron, Nature of proton and Semi-Conductor.

EXCITEMENT OF PHYSICS

👉 Daily life phenomena

👉 Application

👉 Conducting experiment

👉 Future prediction

PHYSICS, TECHNOLOGY AND SOCIETY

Sometimes technology gives rise to new physics; at other times physics generates new technology.

An example of the latter is the wireless communication technology that followed the discovery of the basic laws of electricity and magnetism in the nineteenth century. The

applications of physics are not always easy to foresee. The discipline of thermodynamics arose from the need to understand and improve the working of heat engines. The steam engine, as we know, is inseparable from the Industrial Revolution in England in the eighteenth century, which had great impact on the course of human civilization. 

Another important example of physics giving rise to technology is the silicon ‘chip’ that triggered the computer revolution in the last three decades of the twentieth century.

FUNDAMENTAL FORCES IN NATURE

In our experience, force is needed to push, carry or throw objects, deform or break them. We also experience the impact of forces on us, like when a moving object hits us.

In the macroscopic world, besides the gravitational force, we encounter several kinds of forces: muscular force, contact forces between bodies, friction (which is also a contact force parallel to the surfaces in contact), the forces exerted by compressed or elongated springs and taut strings and ropes (tension), the force of buoyancy and viscous force when solids are in contact with fluids, the force due to pressure of a fluid, the force due to surface tension of a liquid,

and so on.

We know of four fundamental forces in nature.

1. Gravitational Force

2. Electromagnetic Force

3. Strong Nuclear Force

4. Weak Nuclear Force

1. Gravitational Force

(Act between any two masses in the Universe)

The gravitational force is the force of mutual attraction between any two objects by virtue of their masses. It is a universal force. Every object experiences this force due to every other object in the universe.

2. Electromagnetic Force

(Act between charges)

Electromagnetic force is the force between charged particles. In the simpler case when charges are at rest, the force is given by Coulomb’s law : attractive for unlike charges and repulsive for like charges. Charges in motion produce magnetic effects and a magnetic field gives rise to a force on a moving charge. Electric and magnetic effects are, in general, inseparable – hence the name electromagnetic force.                                                                                                                                                                               Gravity is always attractive, while electromagnetic force can be attractive or repulsive. Another way of putting it is that mass comes only in one variety (there is no negative mass), but charge comes in two varieties : positive and negative charge.  It is 10³⁶  times stronger than gravitational force.  

3. Strong Nuclear Force

(Act between n-n, p-p, p-n)

The strong nuclear force binds protons and neutrons in a nucleus. It is evident that without some attractive force, a nucleus will be unstable due to the electric repulsion between its protons. It is charge-independent and acts equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron. Its range is, however, extremely small, of about nuclear dimensions ( 10^-15  m). It is 10³⁸  times stronger than gravitational force.

4. Weak Nuclear Force

(Act between Neutrino and other particle)

 The weak nuclear force appears only in certain nuclear processes such as the β-decay of a nucleus. In β-decay, the nucleus emits an electron and an uncharged particle called neutrino. The weak nuclear force is not as weak as the gravitational force, but much weaker than the strong nuclear and electromagnetic forces. It is 10²⁵  times stronger than gravitational force.

SUMMARY

✅ Physics deals with the study of the basic laws of nature and their manifestation in different phenomena. The basic laws of physics are universal and apply in widely different contexts and conditions.

✅The scope of physics is wide, covering a tremendous range of magnitude of physical quantities.

✅ Physics and technology are related to each other. Sometimes technology gives rise to new physics; at other times physics generates new technology. Both have direct impact on society.

✅There are four fundamental forces in nature that govern the diverse phenomena of the macroscopic and the microscopic world. These are the ‘gravitational force’, the ‘electromagnetic force’, the ‘strong nuclear force’, and the ‘weak nuclear force’. Unification of different forces/domains in nature is a basic quest in physics.

✅ The physical quantities that remain unchanged in a process are called conserved quantities. Some of the general conservation laws in nature include the laws of conservation of mass, energy, linear momentum, angular momentum, charge, parity, etc. Some conservation laws are true for one fundamental force but not for the other.

✅ Conservation laws have a deep connection with symmetries of nature. Symmetries of space and time, and other types of symmetries play a central role in modern theories of fundamental forces in nature.