Newton at the age of twenty-three is said to have seen an apple falling down from tree in his orchid. This was the year 1665. He started thinking about the role of earth's attraction in the motion of moon and other heavenly bodies.
By comparing the acceleration due to gravity due to earth with the acceleration required to keep the moon in its orbit around the earth, he was able to arrive the Basic Law of Gravitation.
In everyday life, gravitation is most commonly thought of as the agency which lends weight to objects with mass.
It is responsible for keeping the Earth and the other planets in their orbits around the Sun;for keeping the Moon in its orbit around the Earth, for the formation of tides; for convection (by which fluid flow occurs under the influence of a temperature gradient and gravity)for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena that we observe.
Gravitation is a natural phenomenon by which objects with mass attract one another.NCERT solutions for class 9 Science prepared by pw will help you to solve your NCERT text book exercise.