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 $M$ are placed at a distance $d$ from each other. What is the gravitational potential $V$ at the point where the gravitational field intensity is zero?

If the gravitational potential on the surface of the earth is $V_0$,then the potential at a point at a height equal to half of the radius of the earth is ..........

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 ..........

Find the potential energy of a system of four particles,each of mass $m$,placed at the vertices of a square of side $l$. Also,obtain the gravitational potential at the centre of the square.

What is the binding energy of a body of mass $m$ lying on the surface of the Earth at a distance $r$ from the center of the Earth?