Fundamental Forces in Nature: The Basic NCERT Concept

In this article, we will be discussing four basic types of natural forces which are responsible for all type of forces we observe namely- Gravitational Force, Electromagnetic Force, Strong Nuclear Force and Weak Nuclear Force.

This article is in continuation to my previous article Physics, Technology and Society: The Basic NCERT Concept . So this is the fourth article of NEPYK Series(A series deeply explaining the concepts of NCERT Physics), in which we will discuss mainly natural forces.

Introduction to Forces

We all have some sort of assumption about the word "Force". We know that we need force to deal with our day-to-day activities. But, to get the proper scientific definition is not easy from our daily activities. Even the famous thinker Aristotle got wrong in doing that. Later Isaac Newton proposed the right one. But all this will be discussed deeply in upcoming chapters.
Here we are going to discuss the natural forces.

What Are Natural Forces?

It is observed that almost all types of force are generated from 4 major forces namely- Gravitational Force, Electromagnetic Force, Strong Nuclear Force and Weak Nuclear Force.
For instance- Friction is generated due to the motion of molecules of the materials due to which electricity and heat are produced. So, we can conclude that friction is the result of electromagnetic force(think of hand-rubbing).

Description of the Four Natural Forces

Gravitational Force

Gravitational force is an attracting force acting between 2 bodies due to their masses. It is a universal force. Each body in the universe experiences a force due to other bodies. For example - motion of planets and each thing on the earth experience a Gravitational force due to gravity. We all have studied about it in ninth standard and will more deeply study in the eighth chapter of the book.
Gravitational force plays a key-role in the large scale phenomena of the universe such as the formation and evolution of stars, galaxies, and galactic clusters.

Properties of Gravitational Force

  1. Range of this force is unlimited and it operates among all the bodies.

  2. It is the weakest natural force.

Electromagnetic Force

It is the force acting among charged bodies. When charges are at rest, the force is expressed in the terms of Coulomb's Law: attractive for unlike charges and repulsive for like charges. Charges in motion produce a magnetic effect and magnetic field gives rise to a force on a moving charge. In general, electric and magnetic effects are inseparable and that is why it is called Electromagnetic Force.

Comparison between Gravitational Force and Electromagnetic Force

Let's compare the two forces:
Gravitational Force

Electromagnetic Force
FE =

where m1,m2 are masses of the two bodies and q1,q2 are charges on the two bodies.
r is the distance between the two bodies.
G and K are universal gravitational and electric force constants respectively.
G= 6.67x10-11Nm2/kg2
K= 9x109Nm2/C2
suppose we compare gravitational and electromagnetic force between two protons:
Let's have some relevant data:
Mass of proton= 1.67x 10-27kg and charge on proton= 1.6x10-19Coulombs.
When we will use the above-mentioned formula, we will find that FE= FGx1036.

Both types of forces have unlimited range theoretically (but practically effects of these fields are observed till certain distance). This leads us to the concept of field (gravitational, electric and magnetic)

The electromagnetic force is stronger and more active than gravitational force because it takes place at much meticulous level. Loss or gain of the electrons causes this force because the other two heavier* elementary particles (proton and neutron) are bounded in the nucleuses of the atoms.

Our day-to-day activities prove that electromagnetic force is much stronger than gravitational. let's see how:
When we lift something suppose a pen, we are lifting it against the force exerted by the large mass of the earth. How is it possible? It is possible due to the electromagnetic force. Now how electromagnetic force is working here? The forces between your hand and the pen are electromagnetic as well as gravitational but the electromagnetic force between atoms of pen and hand is much stronger, and that's why we are able to lift the pen.
*Recent developments have proved that protons and neutrons are built out of still more elementary constituents called quarks.

Strong Nuclear Force

We just talked that protons and neutrons are bounded in the nucleus of the atom but how is it possible as we know there is repulsion between like charges? It is evident that without some attractive force, a nucleus will be unstable due to the electric repulsion between its protons. Because gravitational force is negligible compared to electric force, so it can not be that. Here we need to invoke a new force and that is Strong Nuclear Force. It is a charge independent force and acts equally between a proton and a proton, a proton and a neutron and a neutron and a neutron. Obviously, it must be stronger than electric force otherwise how will it draw over the repulsion caused by electromagnetic force?

Properties of Strong Nuclear Force

  1. It is the strongest among all the 4 natural forces, approximately 100 times stronger than electric force.

  2. It's range is extremely small(10-15m)(nucleus dimensions).

  3. It acts only over nucleus and that's why electrons do not experience it.

Weak Nuclear Force

The weak nuclear force appears only in certain nuclear processes such as β -decay of a nucleus. In β -decay the nucleus emits an electron and an uncharged particle called neutrino.

Properties of Weak Nuclear Force

  1. It has the smallest range(approximately 10-16m).

  2. The weak nuclear force is not as weak as the gravitational force, but much weaker than the strong nuclear and electromagnetic forces.

The ratio of the four natural forces' strength is given by FS:FE:FW:FG = 1039:1037:1026:1
where S, E, W and G represents Strong Nuclear, Electromagnetic, Weak Nuclear and Gravitational respectively.

Towards Unification of Forces

Till now, we should know what unification is. I repeat that briefly what we had discussed in the first article of NEPYK series: Unification is the process to study different scopes or region of the subject under one concept. For example, Newton's Law of gravitation describes falling apple as well as the motion of the moon around the earth, tides etc.

Unification is very helpful in the subject like Physics in which we try to study tons of natural phenomena. Now, we can have some idea of what does the term 'Unification of Forces' mean. It simply means to study different forces under one concept. Towards this, a step is recently taken in 1979 by Sheldon Glashow, Abdus Salam, and Steven Weinburg. They showed that the 'weak' nuclear force and the electromagnetic force could be viewed as the different aspects of the single 'electro-weak' force and the same was experimentally verified by Carlo Rubia and Simon Vander Meer in1984. You can study this deeply here.
Here are the major progressive thoughts in the unification of different forces/domains in nature:

  1. Isaac Newton unified celestial and terrestrial mechanics and showed that the same laws of motion and the law of gravitation apply to both domains(1687).

  2. Hans Christian Oersted(1820) and Michael Faraday(1830) showed that electric and magnetic phenomena are inseparable aspects of a unified domain: Electromagnetism

  3. James Clarke Maxwell(1873) unified electricity, magnetism, and optics by showing that light is an electromagnetic wave .

  4. Another one has been already mentioned above.


Author: neelam joshi30 Jul 2017 Member Level: Gold   Points : 2

It is really a very good article to get an insight of basic concept of force that we study during our school years and very well deals with theoretical concept as well as formula used for those concepts. This article also define how many type of forces are present in nature and how all the forces are responsible for phenomena we see around us. I found the article very useful in gaining knowledge of this concept of physics.

Author: Lovish Raheja30 Jul 2017 Member Level: Silver   Points : 0

Thank you very much for the appreciation Madam.

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