Satellites orbiting 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 force causing the speed of satellite and hence hight 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 arth.
Due to the viscous force acting on satellite, energy decreases continuously and radius of the orbit or height decreases gradually