The gravitational potential energy is maximum at

Four particles $A, B, C$ and $D$ each of mass $m$ are kept at the corners of a square of side $L$. Now the particle $D$ is taken to infinity by an external agent,keeping the other particles fixed at their respective positions. The work done by the gravitational force acting on the particle $D$ during its movement is ..........

Define gravitational potential. Give its unit. Is gravitational potential a vector or a scalar quantity?

If the gravitational potential of an object of mass $m$ on the surface of the Earth is $\phi$,what is the gravitational potential of an object of mass $2m$?

Two particles of mass $m$ and $9m$ are separated by a distance $r$. At a point on the line joining them,the gravitational field is zero. What is the gravitational potential at that point? ($G$ is the universal gravitational constant)

In a certain region of space,the gravitational field is given by $E = -\frac{K}{r}$,where $r$ is the distance from a fixed point and $K$ is a constant. Taking the reference point to be at $r = r_0$ with potential $V = V_0$,the potential at a distance $r$ is: