In our everyday, experience, besides gravitational force, we encounter several kinds of forces like frictional force, the force of buoyancy and viscous force, contact force between the bodies, the force due to surface tension of a liquid and so on.
In later 20th century, we come to know that these different forces occurring in different contexts actually arises from only a small number of fundamental forces in nature.
At the present stage of our understanding, we know four fundamental forces in nature, which are described in brief here.
1.Gravitational Force
Gravitational force is attractive force that acts between any two masses in the universe. Larger the masses and the closer they are, stronger the gravitational attraction between them. It is the force that keeps planets in orbit around the sun, holds galaxies together, and causes objects to fall to the ground on Earth.
Gravitational force is described by Newton’s Law of Universal Gravitation, which states that the force between two masses F is proportional to the product of their masses m1 and m2 and inversely proportional to the square of the distance r between them: F = G m1⋅m2 / r2
Main points of gravitational Force :-
It is the force due to mutual attraction between any two objects
It occurs by virtue of masses of the bodies.
It is universal force and follows inverse square law.
It governs the motion of celestial bodies in universe.
Formation and evolution of stars, galaxies, and galactic clusters due to the gravitational attraction.
2. Electromagnetic Force
Electromagnetic force acts between charged particles. The electromagnetic force can attract or repel depending on the nature of the charges. Like charges repel each other, opposite charges attract. This force is responsible for behavior of electric fields, magnetic fields, and light.
This force is described by Coulomb’s Law for electric charges, and the interaction between electric and magnetic fields is further explained by Maxwell’s equations. Electromagnetic force governs atomic structure, chemical reactions.
Some Points Regarding Electromagnetic Force :-
It is the force due to mutual interaction between the charged particles.
When charges are at rest then force between them are electrostatic. It obeys inverse square law.
It is enormously strong compared to gravity (1036 times the gravitational force).
In general, electric and magnetic effects are inseparable.
Charges in motion produce magnetic effects and give rise to a magnetic force on a moving charge.
3. Strong Nuclear Force
Strong nuclear force is the most powerful force among the four fundamental forces. It acts at the subatomic level, binding protons and neutrons together in the nucleus of an atom. Without the strong force, nuclei would not be stable, as the electromagnetic repulsion between positively charged protons would cause them to fly apart.
This force operates over extremely short distances, roughly on the order of 10−15 meters (the size of a nucleus). Despite its strength, the range of the strong force is limited, making it effective only at nuclear distances.
Key points of Strong force :-
Strong nuclear force of attraction holds together the nucleons (neutrons and protons).
It is the strongest of all fundamental forces and about
10 2 times stronger than electromagnetic force in strength.
It arises due to exchange of sub-nuclear particles, hence very complex in nature.
Nuclear force have the shortest range g upto distance of order of 10-15 m.
It is charge independent.
4. Weak Nuclear Force
Weak nuclear force is responsible for processes like radioactive decay and nuclear fusion. It key role in transforming one type of subatomic particle into another.
One of the primary examples of the weak force is beta decay, where a neutron decays into a proton. This force is weaker than both the electromagnetic and strong forces.
Important points of weak force :-
Weak nuclear force appears only in certain nuclear processes like beta-decay.
It is not as weak as gravitational force but much weaker than the electromagnetic force and strong nuclear force.
The range of weak nuclear force is exceeding small, of the order 10-16
Note :-
1.Four fundamental forces of nature gravitational, electromagnetic, strong nuclear, and weak nuclear are the keystone of physics.
2. Each force governs different aspects of the universe, from the structure of atoms to the motion of planets.
3. Gravity dominates on large space scales and other three forces govern atomic and subatomic interactions.
4. Relative strengths of four type of basic forces in nature can be represented as
FG : FW : FE : FN = 1 :1026 : 1037 : 1039.
5. Each fundamental forces arises due to exchange of characteristic particle called the messenger particle or the field particle.
– For gravitational forces, the field particle is graviton,
– For electromagnetic forces, the field particle is photon
– For strong nuclear forces, the field particle is pi meson.
– For weak nuclear forces, the field particle is vector boson (W+- , Z0).
Four fundamental forces in nature are gravitational force, electromagnetic force, strong nuclear force, and weak nuclear force.
Gravitational force is the weakest of the four forces, but it has an infinite range and is dominant on a space, influencing the motion of planets and stars.
Electromagnetic force acts between charged particles, responsible for actuality like electricity, magnetism, light, and chemical reactions. It is much stronger than gravity and can attract or repel charges.
Strong nuclear force binds protons and neutrons within an atomic nucleus. It is the strongest of the fundamental forces, but it operates only over very short distances (within the nucleus).
Weak nuclear force is responsible for radioactive decay, such as beta decay, and nuclear processes like fusion, which powers stars. It affects subatomic particles and operates over short distances.
Gravity is crucial because it shapes the large-scale structure of the universe, keeping planets in orbit, forming stars and galaxies, and influencing the expansion of the outer space. Its infinite range compensates for its weakness.
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