Four particles,each of mass $M$,are located at the vertices of a square with side $L$. The gravitational potential due to this system at the centre of the square is:

The gravitational field in a region is given by the equation $E = (5\hat{i} + 12\hat{j}) \text{ N/kg}$. If a particle of mass $2 \text{ kg}$ is moved from the origin $(0, 0)$ to the point $(12 \text{ m}, 5 \text{ m})$ in this region, the change in gravitational potential energy is: (in $\text{ J}$)

If $V$ is the gravitational potential due to a sphere of uniform density on its surface,then its value at the center of the sphere will be:

Two bodies of masses $4 \,m$ and $9 \,m$ are separated by a distance $r$. The gravitational potential at a point on the line joining them where the gravitational field becomes zero is:

$A$ particle of mass $10\, g$ is kept on the surface of a uniform sphere of mass $100\, kg$ and radius $10\, cm$. Find the work to be done against the gravitational force between them to take the particle far away from the sphere (you may take $G = 6.67 \times 10^{-11}\, Nm^2 / kg^2$).