Gravitational mass is proportional to gravitational

At what distance from the centre of the moon is the point at which the strength of the resultant gravitational field of the Earth and the Moon is equal to zero (in $,R$)? The Earth's mass is $81$ times that of the Moon,and the distance between the centres of these bodies is $60\,R$,where $R$ is the radius of the Earth.

$3$ particles each of mass $m$ are kept at the vertices of an equilateral triangle of side $L$. The gravitational field at the centre due to these particles is

The gravitational field,due to the 'left over part' of a uniform sphere (from which a part as shown,has been 'removed out'),at a very far off point,$P$,located as shown,would be (nearly)

Define the intensity of the gravitational field and write its equation,unit,and dimensional formula.

Consider two solid spheres of radii $R_{1} = 1 \; m$ and $R_{2} = 2 \; m$ and masses $M_{1}$ and $M_{2}$,respectively. The gravitational field due to sphere $(1)$ and $(2)$ are shown in the graph. The value of $\frac{M_{1}}{M_{2}}$ is