Force due to Gravity on a body

The force due to gravity on a body of mass m kept on the surface of earth of mass M and radius R, is equal to the force of attraction between the earth and that body. It is given as F = (GMm)/(R ^ 2) Taking the mass of earth M = 5.96 * 10 ^ 24 * kg Radius of earth R = 6.37 * 10 ^ 6 m m = 1kg and G = 6.67 * 10 ^ - 11 * N * m ^ 2 / k * g ^ 2 F = 9.8N Then

Thus earth attracts a body of mass 1kg by a force of 9.8 N towards its centre.

Note: As earth attracts an object towards it, the object also attracts the earth towards it by an equal force. Since the object is free to move, it starts moving towards the earth, but the earth because of its large inertia, doesnot move towards the object.

Difference between Gravitation and Gravity :

1. Gravitation is the force of attraction acting between any two bodies of universe Gravity in the earth's gravitational pull on a body, lying on or near the surface of earth.

2. The direction of gravitational force on body A due to body B is along AB. The direction of force of gravity on a body is along the line joining the body and the centre of the earth and is directed towards the centre of the earth.

3. The force of gravitation between two bodies can be zero if the separation between bodies becomes infinity.

The force of gravity on a body is zero at the centre of the earth.