A body is thrown vertically upwards with an initial speed \(\sqrt{gR}\), where \(R\) is the radius of the earth. The maximum height reached by the body from the surface of the earth is:
1. \(\frac{R}{2}\)
2. \(\frac{3R}{2}\)
3. \(R\)
4. \(\frac{R}{4}\)

A particle is located midway between two point masses each of mass \(M\) kept at a separation \(2d.\) The escape speed of the particle is:
(neglecting the effect of any other gravitational effect)
1. \(\sqrt{\frac{2 GM}{d}}\)
2. \(2 \sqrt{\frac{GM}{d}}\)
3. \(\sqrt{\frac{3 GM}{d}}\)
4. \(\sqrt{\frac{GM}{2 d}}\)

Three identical particles each of mass \(M\) are located at the vertices of an equilateral triangle of side \(a\). The escape speed of one particle will be:
1. \(\sqrt{\frac{4 GM}{a}}\)
2. \(\sqrt{\frac{3 GM}{a}}\)
3. \(\sqrt{\frac{2 GM}{a}}\)
4. \(\sqrt{\frac{GM}{a}}\)

Two identical hollow spheres of negligible thickness are placed in contact with each other. The force of gravitation between the spheres will be proportional to (\(R\) = radius of each sphere):
1. \(R\)
2. \(R^2\)
3. \(R^4\)
4. \(R^3\)

A planet is revolving around a massive star in a circular orbit of radius \(R\). If the gravitational force of attraction between the planet and the star is inversely proportional to \(R^3,\) then the time period of revolution \(T\) is proportional to:
1. \(R^5\)
2. \(R^3\)
3. \(R^2\)
4. \(R\)

When a planet revolves around the sun in an elliptical orbit, then which of the following remains constant?

A satellite of mass \(m\) revolving around the earth in a circular orbit of radius \(r\) has its angular momentum equal to \(L\) about the centre of the earth. The potential energy of the satellite is: 
1. \(- \frac{L^{2}}{2 mr}\)
2. \(- \frac{2L^{2}}{mr^2}\)
3. \(- \frac{3L^{2}}{m^2r^2}\)
4. \(- \frac{L^{2}}{mr^2}\)