(a)[2]
Write down the equation for the gravitational force $F$ acting between two point masses $m_1$ and $m_2$ when they are separated by a distance $r$. State the meaning of any other symbols you choose to use.
(b)[3]
A satellite travels in a circular orbit of radius $R$ around a planet of mass $M$. Show that the orbital period $T$ satisfies $T^2 = kR^3$, where $k$ is a constant that depends on the value of $M$. Give your reasoning.
(c(i))[2]
A satellite moves in a circular orbit around the Earth with a period of $24$ hours. The Earth has mass $6.0 \times 10^{24}\,\text{kg}$. Calculate the radius of the orbit.
(c(ii))[2]
State the two additional conditions needed for the orbit to be geostationary.