Earth’ gravitational force :
- The earth attracts every object near it towards itself because of the gravitational force.
- The centre of mass of the earth is situated at its centre, so the gravitational force on any object due to the earth is always directed towards the centre of the earth.
- Because of this force, an object falls vertically downwards on the earth.
- Similarly, when we throw a stone vertically upwards, this force tries to pull it down and reduces its velocity.
- Due to this constant downward pull, the velocity becomes zero after a while.
- The pull continues to be exerted and the stone starts moving vertically downward towards the centre of the earth under its influence.
- Thus, if the earth attracts an apple towards itself, the apple also attracts the earth to-wards itself with the same force.
- The gravitational force due to the earth also acts on the moon because of which it revolves around the earth.
- Similar situation exists for the artificial satellites orbiting the earth.
- The moon and the artificial satellites orbit the earth.
- Due to velocity of the moon and the satellites along their orbits, they do not fall on the earth.
- If this velocity was not there, they would have fallen on the earth.