Q.Explain in detail the four fundamental forces.

All physical interactions observed in nature, however varied they may look on the surface, are now understood to be governed by exactly four fundamental forces, each dominant in its own particular regime.

Gravitational force, a universal attractive force acting between any two masses, is by far the weakest of the four forces at the scale of individual particles, but because it always adds up (never cancels, unlike electric charge) it dominates over astronomical distances - it is what keeps the planets, including Earth, bound in orbit around the Sun.

Electromagnetic force acts between electric charges (and, through moving charges, magnetic sources), and is responsible for the great majority of everyday physical and chemical phenomena. It is, specifically, the electromagnetic repulsion between the atoms making up our feet and the atoms making up the ground that lets us stand on the Earth's surface at all, rather than any deeper form of direct contact.

Strong nuclear force is short-range but, within that range, by far the strongest of the four forces; it acts attractively between nucleons (protons and neutrons) and is exactly what holds the nucleus together against the fierce electrostatic repulsion among its protons. It is this force that keeps the atoms making up our own bodies stable and intact. …