Question:
Find the acceleration due to gravity of the moon at a point $1000 \mathrm{~km}$ above the moon's surface. The mass of the moon is $7.4 \times 10^{22} \mathrm{~kg}$ and its radius is $1740 \mathrm{~km}$.
Solution:
The acceleration due to gravity at a point at height ' $h$ ' from the surface of moon of radius $R$ is
$g=\frac{\mathrm{GM}}{(\mathrm{R}+\mathrm{h})^{2}}$
$=\frac{6.67 \times 10^{-11} \times 7.4 \times 10^{22}}{(1740+1000)^{2} \times 10^{6}}$
$=0.65 \mathrm{~m} / \mathrm{s}^{2}$