Satellite orbitting the earth have finite life and sometimes debris of satellites fall to the earth. This is because

Options

A. the solar cells and batteries in satellites run out
B. the law of gravitation predict a trajectory spiralling inwards
C. of viscous forces causing the speed of satellite and hence height to gradually decrease
D. of collisions with other satellites

Answer

C

Explanation

As the total energy of the earth satellite bounded system is negative `((-GM)/(2a))`, where a is radius of the satellite and M is mass of the earth. Due to the viscous force acting on satellite, energy decreases continuously and radius of the orbit or height decreases gradually.