1. The distance of the centres of moon and earth is D. The mass of earth is 81 times the mass of the moon. At what distance from the centre of the earth, the gravitational force will be zero

2. Two identical solid copper spheres of radius R placed in contact with each other. The gravitational attraction between them is proportional to 

3. The mass and diameter of a planet have twice the value of the corresponding parameters of earth. Acceleration due to gravity on the surface of the planet is

4. At what altitude in metre will the acceleration due to gravity be 25% of that at the earth's surface (Radius of earth = R metre)      

5. The height of the point vertically above the earth’s surface, at which acceleration due to gravity becomes 1% of its value at the surface is (Radius of the earth = R)

6.A body of mass m kg. starts falling from a point 2R above the Earth’s surface. Its kinetic energy when it has fallen to a point ‘R’ above the Earth’s surface [R-Radius of Earth, M-Mass of Earth, G-Gravitational Constant]

7. The mass of the earth is 81 times that of the moon and the radius of the earth is 3.5 times that of the moon. The ratio of the escape velocity on the surface of earth to that on the surface of moon will be

8. In a satellite if the time of revolution is T, then K.E. is proportional to                                                             

9. The earth revolves round the sun in one year. If the distance between them becomes double, the new period of revolution will be

10.An artificial satellite moving in a circular orbit around the earth has a total (kinetic + potential) energy E₀. Its potential energy is