Question

Geo-stationary satellite is one which

• A. Remains stationary at a fixed height from the eath's surface
• B. Revolves like other satellites but in the opposite direction of eath's rotation
• C. Revolves round the earth at a suitable height with same angular velocity and in the same direction as earth does about its own axis
• D. None of these

Answer 1

The correct option is C Revolves round the earth at a suitable height with same angular velocity and in the same direction as earth does about its own axis

Geostationary satellites are also called synchronous satellite. They always remain about the same path on equator, i.e., it has a period of exactly one day $\left(86400\right)$
So orbit radius $[T=2\pi \sqrt{\frac{r^3}{GM}}]$ comes out to be $42400$ km, which is nearly equal to the circumference of earth. So height of Geostationary satellite from the earth surface is $42,400-6400=36,000$km.