(a)[2]
State the formula for the gravitational force $F$ acting between two point masses $m_1$ and $m_2$ when they are separated by a distance $r$. State what any other symbols mean.
(b)[3]
A satellite moves 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 $M$. Explain your reasoning.
(c(i))[2]
A satellite travels in a circular orbit around the Earth with a period of $24$ hours. The mass of the Earth is $6.0 \times 10^{24}\,\text{kg}$. Calculate the radius of the orbit.
(c(ii))[2]
State the two further conditions that must be satisfied for an orbit to be geostationary.