A geo-stationary stellite orbits around the earth in a circular orbit of radius 36,000km. Then, the time period of a spy stellite orbitting a few hundred km above the earth's surface `(R_(earth) = 6400km)` will approximately be

Explanation

Here, `r_(1) = 36000 km , r_(2) ~~ 6400 km`,
`T_(1) = 24 h, T_(2) = ?`
`T_(2) = T_(1) ((r_(2))/(r_(1)))^(3//2) = 24 ((6400)/(36000))^(3//2) = 1.8 h`