Gravitation for JEE Main 2026: Complete Guide

Gravitation is a moderate-weightage chapter that contributes one to two questions per JEE Main session. The chapter is conceptually unified — everything flows from Newton's law of universal gravitation — which means mastering the fundamentals unlocks nearly every problem type. The topics JEE Main tests most heavily are gravitational potential energy and escape velocity, orbital mechanics and Kepler's laws, and satellite behavior. This guide builds each concept systematically and links them to the problem types that appear most often.

Newton's Law of Universal Gravitation

Newton's law states that every two masses attract each other with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. For a spherically symmetric body, all the mass can be treated as concentrated at the center. Inside a uniform shell, the gravitational field is zero; outside it is the same as if the shell were a point mass. These two results resolve most problems involving spherical cavities and layered planets.

The acceleration due to gravity at Earth's surface follows from Newton's law. Variations of g — with altitude, depth, latitude, and Earth's rotation — are among the most frequently tested quantitative problems. Master the formula for variation with altitude and the linear decrease with depth. Connect this chapter to our mechanics guide for the dynamics foundations.

Gravitational Field and Potential

The gravitational field at a point is the force per unit mass that a test mass would experience there. The gravitational potential is the work done per unit mass in bringing a test mass from infinity to that point; it is always negative near a real mass. JEE Main tests the relationship between field and potential — field is the negative gradient of potential — and problems requiring you to find the potential or field due to combinations of masses.

The potential energy of a two-body system is negative G times the product of the masses divided by the separation. The distinction between gravitational potential and gravitational potential energy is a common source of errors. Take a free mock test on gravitation to check your fluency.

Escape Velocity and Binding Energy

Escape velocity is the minimum speed at which an object must be launched from a planet's surface to escape to infinity without further propulsion, derived by setting total mechanical energy to zero. The result depends on the mass and radius of the planet but not the projectile mass. JEE Main tests numerical calculations of escape velocity and comparisons between planets.

The binding energy of an orbiting satellite is half the magnitude of its potential energy, a result that follows from the virial theorem. Problems comparing the energy required to launch a satellite to different orbits require careful bookkeeping of the total mechanical energy, and JEE Main tests these comparisons regularly.

Orbital Mechanics and Kepler's Laws

A satellite in a circular orbit moves at constant speed. The orbital velocity follows from the condition that gravitational force provides the centripetal acceleration. Higher orbits have lower speeds and longer periods, but greater total energy — a counterintuitive result worth understanding deeply.

Kepler's three laws: orbits are ellipses with the Sun at one focus, equal areas are swept in equal times, and the square of the orbital period is proportional to the cube of the semi-major axis. JEE Main tests the third law quantitatively and the second law for comparing speeds at different points in an elliptical orbit. The second law is a direct consequence of angular momentum conservation.

Geostationary and Polar Satellites

A geostationary satellite orbits in the equatorial plane with a period of 24 hours, appearing stationary from Earth's surface. JEE Main tests the radius of the geostationary orbit and the conditions for geostationary motion. The distinction between geostationary and polar satellites and their applications appears in conceptual questions.

Revision Strategy

Master Newton's law and the shell theorem first, then work through gravitational potential and field before tackling orbital mechanics. This chapter integrates with energy and rotational concepts from our rotational motion guide. Build it into the first week of your 30-day plan alongside mechanics. Sign up free to access our curated gravitation question bank.