Use Newton’s law of gravitation to show that the gravitational field strength 
at a distance 
away from a point mass 
is given by
The Earth has a mass of 
, and a radius of 
. The Moon has a mass of 
and a radius of 
. The Earth and the Moon can both be considered as point masses at their centres. Their centres are a distance of 
apart.
Show that the gravitational field strength at the surface of the Moon due to the mass of the Moon is 
.
Explain why there is a point X on the line between the centres of the Earth and the Moon where the resultant gravitational field strength due to the Earth and the Moon is zero.
Calculate the distance 
of point X from the centre of the Moon.
.
