# Universal law of gravitation, gravity, acceleration due to gravity

Newton’s law of universal gravitation states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Gravitation

Gravitation is the force by which every mass or particle of matter, including photons, attracts and is attracted by every other mass or particle of matter.The gravitational field at any point P in space is defined as the gravitational force felt by a tiny unit mass placed at P.

Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.

Mathematically, this law, and the magnitude of the force due to the gravitational interaction between two particles, is expressed with :-

Properties of Gravitational Force.

 It is always attractive in nature while electric and magnetic force can be attractive or repulsive.

 It is independent of the medium between the particles while electric and magnetic force depend on the nature of the medium between the particles.

 It holds good over a wide range of distances. It is found true for interplanetary to inter atomic distances.

 It is a central force i.e. acts along the line joining the centres of two interacting bodies.

 It is a two-body interaction i.e. gravitational force between two particles is independent of the presence or absence of other particles.

 It is the weakest force in nature : As Fnuclear > F electromagnetic > F gravitational .

 It is a conservative force i.e. work done by it is path independent or work done in moving a particle round a closed path under the action of gravitational force is zero.

 It is an action reaction pair i.e. the force with which one body (say earth) attracts the second body (say moon) is equal to the force with which moon attracts the earth.

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