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

A planet moving along an elliptical orbit is closest to the sun at a distance r₁ and farthest away at a distance of r₂. If $$v$$₁ and $$v$$₂ are the linear velocities at these points respectively, then the ratio $${{{v_1}} \over {{v_2}}}$$ is

The additional kinetic energy to be provided to a satellite of mass m revolving around a planet of mass M, to transfer it from a circular orbit of radius R₁ to another of radius R₂(R₂ > R₁) is

(1)   Centre of gravity (C.G) of a body is the point at which the weight of the body acts
(2)   Centre of mass coincides with the centre of gravity if the earth is assumed to have infinitely large radius.
(3)   To evaluate the gravitational field intensity due to any body at an external point, the entire mass of the body can be considered to be concentrated at its C.G.
(4)   The radius of gyration of any body rotating about an axis is the length of the perpendicular dropped from the C.G. of the body to the axis.

Which one of the following pairs of statements is correct ?