Every object in the universe attracts every other object with a force which is inversely proportional to 

What will be the weight of an object at the centre of the earth ?

The acceleration due to gravity is zero at

If the masses of both the object are doubled, the gravitational force of attraction is

For a freely falling body (falling vertically down wards) 'g' is

The minimum velocity that an object should possess to escape from the gravitational field of earth is called

Examples of unstable equilibrium is

Name the fundamental force which holds the planets in their orbits around the sun:

Satellites whose period of revolution is 24 hours are called

The velocity of freely falling object at the end of 8 seconds is