(a)[3]
Explain the meaning of a geostationary orbit.
(b)[4]
A satellite of mass $m$ moves in a circular orbit around a planet. The planet’s mass $M$ may be taken to be concentrated at its centre. Show that the radius $R$ of the satellite’s orbit is given by the expression $R^3 = \left(\frac{G M T^2}{4\pi^2}\right)$ where $T$ is the period of the satellite’s orbit and $G$ is the gravitational constant. Explain your working.
(c)[3]
The mass of the Earth is $6.0 \times 10^{24} \text{ kg}$. Use the expression given in (b) to find the radius of the geostationary orbit about the Earth.