(a)[2]
Show that the gravitational field strength at the surface of the planet is $3.7\,\text{N kg}^{-1}$.
(b)[3]
A stone of mass $2.4\,\text{kg}$ is lifted from the surface of the planet through a vertical height of $1800\,\text{m}$. Use the field strength value from (a) to find the change in gravitational potential energy of the stone. Show your working.
(c)
A rock, initially at rest at infinity, moves towards the planet. At point $P$, its height above the surface of the planet is $3.5D$, where $D$ is the diameter of the planet, as shown in Fig.$\,1.1$.