1.Two satellite move in circular orbits around the Earth at distance 9000 km and from the centre of Earth. If the nearer satellite has a period of revolution of 90 minutes around the Earth, then the difference in the period of revolution around the Earth is

2.What is the weight of a body at a distance 2r from the centre of the Earth if the gravitational potential energy of the body at a distance r from the centre of the Earth is U ?

3.The diameters of two planets are in the ratio of 4 : 1. Their mean densities are in the ratio 1 : 2. The ratio of accelerations due to gravity on the planets is

4.If the Earth suddenly shrinks to half of its present radius, then the acceleration due to gravity will be

5.The increase in gravitational potential energy of an object of mass m raised from the surface of Earth to a height equal to the radius R of Earth is