Four particles each of mass $m$ are placed at the vertices of a square of side $l.$ The potential energy of the system is

If one wants to remove all the mass of the earth to infinity in order to break it up completely. The amount of energy that needs to be supplied will be $\frac{x}{5}\, \frac{ GM ^{2}}{ R }$ where $x$ is $\quad\,……….$ (Round off to the Nearest Integer)

($M$ is the mass of earth, $R$ is the radius of earth, $G$ is the gravitational constant)

If three particles each of mass $M$ are placed at the corners of an equilateral triangle of side $a$ , the potential energy of the system and the work done if the side of the triangle is changed from $a$ to $2a$ , are

If radius of an orbiting satellite is decreased, then its kinetic energy

A particle of mass $m$ is thrown upwards from the surface of the earth, with a velocity $u.$ The mass and the radius of the earth are, respectively, $M$ and $R.$  $G$ is gravitational constant and $g$ is acceleration due to gravity on the surface of the earth. The minimum value of $u$ so that the particle does not return back to earth, is