1.A communication satellite is put in an orbit around the Earth. What is the approximate time taken by a radiowave to go to the satellite and come back to the Earth ?

2.A uniform spherical shell gradually shrinks maintaining its shape. The gravitational potential at the centre

3.The kinetic energy needed to project a body of mass m from the Earth s surface to infinity is

4.The gravitational potential difference between the surface of a planet and a point 20 m above the surface, is 2 joule/kg. If the gravitational field is uniform, then the work done in carrying a 5 kg body to a height of 4 m above the surface is

5.A missile which missed its target went into orbit around the Earth at a mean radius 4 times as great as the parking orbit of a satellite. The period of the missile is