When an object is brought from infinity to a distance $r$ from a mass,its gravitational potential energy ....... . (Fill in the blank)

Two bodies of masses $m$ and $9m$ are placed at a distance $r$. The gravitational potential at a point on the line joining them,where the gravitational field is zero,is ($G$ is the universal gravitational constant).

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:

In a certain region of space,the gravitational field is given by $E = -k/r$,where $r$ is the distance and $k$ is a constant. If the gravitational potential at $r = r_0$ is $V_0$,then what is the expression for the gravitational potential $V$?

$A$ 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 $G = 6.67 \times 10^{-11}\, Nm^2 / kg^2$).

The gravitational potential energy of a system of three masses $m$,$2m$,and $3m$ placed at the three vertices of an equilateral triangle of side '$a$' is: