$A$ body of mass $m$ is kept at a small height $h$ above the ground. If the radius of the earth is $R$ and its mass is $M$,the potential energy of the body and earth system (with $h = \infty$ being the reference position) is

The gravitational field due to a mass distribution is $E = K/x^3$ in the $X$-direction ($K$ is a constant). Taking the gravitational potential to be zero at infinity,its value at a distance $x$ is:

Two heavy spheres each of mass $100 \; kg$ and radius $0.10 \; m$ are placed $1.0 \; m$ apart on a horizontal table. What is the gravitational force and potential at the mid-point of the line joining the centres of the spheres? Is an object placed at that point in equilibrium? If so,is the equilibrium stable or unstable?

Potential energy of a satellite having mass $m$ and rotating at a height of $6.4 \times 10^6 \ m$ from the Earth's surface is

Calculate the energy needed to move a mass of $4 \, kg$ from the center of the Earth to its surface (in joules),given that the radius of the Earth is $6400 \, km$ and the acceleration due to gravity at the surface of the Earth is $g = 10 \, m/s^2$.

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