The Physical World

Physics is an essential part of science concerned with understanding natural occurrences that take place in our universe. It includes many fields, such as mechanics, electromagnetism, thermodynamics, modern physics, etc. Around 1600 and 1900, three wide branches developed–classical mechanics, thermodynamics, and electromagnetism–and together, they are called classical physics. In 1905, it became noticeable that classical physics notions failed to clarify several phenomena. Thereafter, new theories originated, such as special relativity, quantum mechanics, etc., and these came to be known as Modern Physics 

Physics

Physics is the study of nature’s law and representation in different natural occurrences. Physics is the analysis of the physical world around us, as well as matter and motion.

• The word “physics” comes from the Greek word phusikḗ, meaning nature.
• In physics, there are two principal types of approaches:
  • Unification: This approach assumes all of the world’s happenings as an exhibition of universal laws in different forms and conditions. For instance, the law of gravitation involves the motion of planets. Electromagnetic laws govern all electric and magnetic occurrences.
  • Reduction: This is an approach to emanate properties of complex systems from the properties and relations of their constituent parts. For instance, in thermodynamics, we study temperature which is related to the average kinetic energy of molecules in a kinetic theory.

Effects and Importance of Physics

• Phenomena that take place over a large magnitude can be defined with simple theory.
• Experiments and observations are used to develop new theories for anonymous phenomena and improve old theories for existing phenomena.
• Evolution of devices using laws of physics.

Physics is broadly categorised into two types–classical physics and modern physics.  Modern physics deals with microscopic phenomena, whereas classical physics deals with macroscopic phenomena.

The macroscopic field comprises phenomena of large hierarchies such as environmental, terrestrial, and astronomical. It consists of the following subjects:

• Newton’s laws of motion and gravity–Mechanics. For example,
  • in the propulsion of missiles and rockets by ejecting gases
  • water/sound waves
  • the equilibrium of a rod bending, when a load is put on it

• Electric and magnetic phenomena are related to charged and magnetic entities–Electromagnetics. For example,
  • the motion of a current-carrying conductor in a magnetic field
  • the response of a circuit to an AC voltage (signal)
  • the propagation of radio waves in the ionosphere

• Optics deals with phenomena that involve light. For example,
  • Refraction and Reflection of light
  • Dispersion of light through a prism
  • Colour exhibited by thin films

The microscopic domain contains phenomena at miniature scales like atomic, molecular, and nuclear. Simultaneously, it is also associated with the interaction of probes like electrons, photons, and other elementary particles. Quantum theory has been devised to define these phenomena.

• Thermodynamics – It deals with systems in macroscopic balance and changes in internal energy, temperature, entropies, etc. For example,
  • The efficiency of heat engines
  • The direction of physical and chemical processes

Factors Responsible for the Progress of Physics

• Qualitative examination and quantitative analysis
• Application of universal laws in various contexts
• In the approximation approach (complex phenomena split into a group of basic laws)
• In focusing on and extracting essential features of natural occurrences

Fundamental Forces in Nature

In our day-to-day life, we experience forces like frictional force when walking, the gravitational force due which we are able to live on earth, electro-Magnetic forces in the motor of vehicles, a muscular force for pulling and pushing the box, sometimes in elongation of spring and compression of spring.Sometimes electric forces in rubbing a piece of cloth and nuclear forces due to intermolecular force of attraction and repulsion. All these forces constitute fundamental forces of nature.

Some fundamental forces like:

1. The gravitational force of mutual attraction between two objects by virtue of their masses. 
2. Electromagnetic force is the force between charged particles. Charges at rest have electric attraction and repulsion. Charges in motion create magnetic force. Jointly they are called electromagnetic forces.
3. In the nucleus, the repulsive and attractive force between the neutrons and protons is known as strong nuclear force. The strong nuclear force is charge independent and acts between the proton-neutron, proton-proton, and neutron-neutron.
4. Weak nuclear force: This force arises only in certain nuclear processes such as the β-decay of the nucleus. In β-decay, the nucleus ejects an electron and an uncharged particle called the neutrino. 

Conserved Quantities

Physics provides laws to outline investigations and observations of the phenomena occurring in the universe.

• Physical quantities which are constant with time are known as conserved quantities. For instance, when an external force is applied on a body, kinetic and potential energy alters over time, whereas the total mechanical energy (kinetic + potential) stays constant.
• Conserved quantities can be a scalar (energy) or vector (total linear momentum and total angular momentum).

Conservation Laws

A conservation law is an assumption established on observance and experimentations which cannot be proved. These can be confirmed via experiments.

In the conservation of energy

• According to the fundamental law of the conservation of energy, energies stay constant over time and are altered from one form to another.
• The law of conservation of energy is applicable in the universe and it is assumed that the total energy of the universe stays unchanged.
• Under identical conditions, nature delivers symmetric results at different times.

Conservation of mass

In chemical reactions, this principle is used for examination.

The chemical reactions involved are primarily a rearrangement of atoms among dissimilar molecules.

• In exothermic reactions, the total binding energy of molecules is less than the total binding energy of the product molecules and heat is the by-product.
• The converse is true for energy-absorbing (endothermic) reactions.
• Generally, atoms are simply rearranged but not destroyed, the total mass of the reactants is equal to the total mass of the products in a chemical reaction.
• In  Einstein’s theory, mass is related to energy.

Law of conservation of linear momentum

• The symmetricity of laws of nature with respect to translation in space is generally known as the law of conservation of linear momentum.
• For instance, the law of gravitation is the same on earth and even on the moon, the acceleration due to gravity on the moon is 1/6th  of that on earth.

Law of conservation of angular momentum

• The isotropy of space represents the law of conservation of angular momentum.

Conclusion

Physics is a constituent of science that includes an analysis of the physical world, such as the relation between energy and matter. Energy is the fictional system that gives us an idea about how the universe functions and accounts for changes in matter. We know that energy can be changed from one form to another. It is converted by physical events. Universal law states that energy can neither be created nor be destroyed. When transformed, usually some amount of it gets converted as heat. By learning physics, we can comprehend the physical world more clearly. Physics can be defined as the science of measurement. The purpose of physics is to utilise basic concepts, equations, and hypotheses to define the physical world.