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 laws of gravitational perdict a trajectory spiralling inwards.
C. of various forces causing the speed of satellite and hence height to gradually decrease.
D. of collisions with other satellites.

Answer

C

Explanation

Orbital velocity of satellite at distance `r` from the centre of earth is, `upsilon = sqrt((GM)/(r ))`
Total energy of satellite `= PE + KE = - (GM m)/(r ) + (1)/(2) m upsilon^(2) = - (GM m)/(r ) + (1)/(2) m (GM)/(r ) = - (GM m)/(2r)`
The viscous force acting on satellite decreases the energy of satellite. as a result of it, the total energy of satllite becomes more negative. Therefore, the value of `r` gradually decreases, consequently the height of satellite graduallty decreases.