21.The ratio of the radius of the Earth to that of moon is 10. The ratio of acceleration due to gravity on Earth and on Moon is 6. The ratio of the escape velocity from the surface of Earth to that from the Moon is

22.The gravitational potential energy of a body of mass m at a distance r from the centre of the Earth is U. What is the weight of the body at this distance ?

23.The radius of the Earth shrinks by 1%, its mass remaining the same. The percentage change in the value of g is

24.Suppose Moon s orbital motion around the earth is suddenly stopped. What time the Moon shall take to fall on to the Earth ?

25.The value of g at a certain height h above the free surface of Earth is x / 4 where x is the value of g at the surface of Earth. The height h is