Fundamental Forces of Nature: A force, as we know, is a push or a pull that can cause an object at rest to move or can bring a change in the direction or speed of a moving object. A force is required to bring a change in the state of motion of a body. From throwing a ball to walking on the ground, from launching a satellite to picking a needle, forces act all around us. We can not imagine our lives without these physical forces. Most of these forces can be associated with the basic interaction between molecules, but some can not be reduced to these elementary interactions. Such forces are called Fundamental Forces in nature. Let us learn in detail about the nature and types of these fundamental forces.

What is a Fundamental Force?

A fundamental force, also known as fundamental interaction, describes the nature of attraction or repulsion between objects based on the interactions between fields and particles. These forces are responsible for how matter behaves, and these interactions can not be reduced to basic interactions. All the known physical forces can be reduced down to these fundamental forces. The interaction between particles or objects and the decay of certain particles are governed by these fundamental forces.

Types of Fundamental Forces in Nature

We can characterize the fundamental forces based on the following four features:

• 1. The types of particles that are experiencing the force
• 2. The nature of the particles mediating the force
• 3. The relative strength of the force acting between the particles
• 4. The effective range over which effect of force can be felt.

Based on these categories, the types of fundamental forces are:

• 1. Gravitational force
• 2. Electromagnetic force
• 3. Strong nuclear force
• 4. Weak nuclear force

Gravitational Force

Gravitational force is the force that holds the world in its state. It is an attractive force. It is the reason why we do not float, why everything falls, why planets move their orbits, or why we can stand on the ground. It is the force of attraction acting between all the bodies in the universe. It is a long-range force because it acts between heavenly bodies that are millions of miles apart, the reason why the planets in our solar system hold their positions around the sun. The gravitational force is strong when considered for massive objects, like the sun or giant planets. But on an atomic level, gravitation is considered to be a weak force; in fact, it is the weakest of the four fundamental forces. The force of gravity was discovered by Newton. According to him, the force of gravitation between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Mathematically, the force of gravity between two bodies of masses \({m_1}\) and \({m_2}\), kept \(r\) distance apart in a vacuum, can be given as
\({F_g} = \frac{{G{m_1}{m_2}}}{{{r^2}}}\)
Where \(G = 6.67408 \times {10^{ – 11}}\;{{\rm{m}}^3}\;{\rm{k}}{{\rm{g}}^{ – 1}}\;{{\rm{s}}^{ – 2}}\) is the universal gravitation constant.

Importance of gravity:

• 1. Gravity is the force that pulls objects to the earth’s surface and prevents everything on the earth from moving apart. It is crucial for the survival of life.
• 2. The gravitational forces between the sun and other planets hold the entire solar system in a stable position.
• 3. In the absence of gravity, the earth will not be able to hold its atmosphere like the other planets, and there will be no air to breathe.
• 4. It is by virtue of gravitational force that the moon revolves around the surface of the earth.

Electromagnetic Force

Consider the case of an atom; electrons, protons and neutrons are enclosed in such a small space, where protons and neutrons are present in the dense nucleus while electrons orbit in the shells outside the nucleus. The forces acting between the particles at the subatomic level follow a different set of rules than the macroscopic particles. The electromagnetic forces describe the interaction between these charges. In the 19th century, James Maxwell stated that like charges repel while unlike charges attract each other. Thus, unlike gravitational force, this force can be both repulsive and attractive.  Electromagnetic forces are the forces that act between charged particles. Rub a plastic scale on your head and bring it close to bits of paper; the bits of paper get attracted to it. This is nothing but an example of electromagnetic force. These are short-range forces meaning that their effect decreases as the distance between the charged particles increases. These forces are considered to be strong forces. The magnitude of these forces can be calculated using the coulomb’s law, which states that the forces acting between two charges are directly proportional to the product of the two charges and inversely proportional to the distance between them. The expression for the coulomb’s force can be given as:

\({F_c} = \frac{{kqQ}}{{{r^2}}}\)

Where \({F_c}\) is the coulomb’s force, \(q\) and \(Q\) are two charges, \(r\) is the distance between the charges, and \(k\) is the constant of proportionality.

Importance of electromagnetic force:

• 1. As the magnitude of electrostatic forces is quite enormous at the atomic and molecular levels, these forces are significantly stronger than the gravitational force when compared at that level.
• 2. These forces are the reason behind the functioning and stability of atoms. It also serves macroscopic forces like tension, friction, normal force and spring forces.
• 3. The phenomena of lightning and electricity are associated with the flow of charges and can be understood with the help of electrostatic forces.

Strong Nuclear Force

The force acting between the protons and neutrons within the nucleus of an atom are called strong nuclear forces. These strong nuclear forces are responsible for the stability of the nucleus; these forces tend to minimize the repulsive forces acting between protons and neutrons. These are the strongest fundamental forces, and these forces are attractive in nature. Strong nuclear forces act between neutron-proton, proton-proton and neutron-neutron. Thus, these are not dependent on the charge of the subatomic particle. These forces are short-range forces, and they act in the range of just \({10^{ – 15}}\;{\rm{m}}\). The repulsion forces between the protons can lead to the collapse of an atomic nucleus in the absence of these strong nuclear forces. Here it is important to remember that these forces do not act between electrons.

Importance of strong nuclear force:

• 1. These forces ensure the overall stability of the atomic nucleus.
• 2. These forces are used for understanding the electrostatic theory.

Weak Nuclear Force

A weak nuclear force can be defined as the force that acts between elementary particles that cause specific processes to occur even at a low probability, like radioactive decays involving the emission of \(β\) particles. These types of interaction are possible by the exchange of force-carrying particles that are generally known as bosons. Weak nuclear forces are stronger than the force of gravitation but weaker compared to the electromagnetic forces.

Specific kinds of bosons are responsible for the weak, electromagnetic, and strong forces.

Importance of Weak nuclear force:

• 1. Unlike the other fundamental forces, these forces do not follow parity symmetry.
• 2. Unlike the other fundamental forces, these forces do not follow charge-parity symmetry.
• 3. These forces cause the conversion of quarks into other forms.
• 4. The propagation of weak nuclear forces is associated with carrier particles having a considerable mass.

Summary

Fundamental forces connect the forces that govern our day to day life. These forces are responsible for all the macro and microscopic activities that happen around us. Starting from gravity, it is the force that governs the behaviour of objects with respect to each other. Such objects can be of the size of a cricket ball or even earth and moon. But when we shrink the size of objects to an atomic level, gravity is certainly not the dominant force. Electromagnetic forces come into play at the atomic and molecular levels. These forces act between charges like electrons and help us understand the phenomena associated with the motion of these charges. When we further reduce the size of an object to the nuclear size, gravitation and electromagnetic forces are certainly not sufficient to maintain the overall stability of the nucleus within an atom. Strong nuclear forces counteract the repulsive forces acting between the protons or proton-neutron or neutrons. Thus, gravity binds the universe, electromagnetic force binds the matter, and strong nuclear force binds the atom. The weak nuclear force comes into play in certain special reactions with a very low chance of occurring. These forces are responsible for radioactive processes, especially the beta decay neutrino interactions.

Frequently Asked Questions on Fundamental Forces of Nature

Q.1. Which is the strongest fundamental force?
Ans: The strong nuclear force is the strongest fundamental force.

Q.2. What are fundamental forces?
Ans: Fundamental forces are the forces that can not further be reduced to other basic forces.

Q.3. Which force explains the radioactive decay especially involving beta particles?
Ans: The weak nuclear forces are responsible for such low probability processes.

Q.4. Name the force responsible for an apple falling from a tree.
Ans: The force responsible for an apple falling from a tree is the force of gravitation.

Q.5. Which force is responsible for the flow of electric current?
Ans: The flow of electric current is due to electromagnetic forces.

Q.6. How many fundamental forces are there in nature?
Ans: There are four fundamental forces in nature.

Q.7. Which is the weakest fundamental force?
Ans: Gravity is the weakest fundamental force.

CBSE NCERT Solutions For Chapter: Physical World

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