Answer the following questions related to gravitational interaction.
(i) State Newton’s universal law of gravitation.
(ii) Define gravitational field intensity at a point in space.
(iii) Explain the principle that allows you to obtain the net gravitational field when more than one mass is present.
(iv) Two identical point masses are fixed at points A and B that are d metres apart on a straight line. Using a neat sketch, describe qualitatively how the magnitude of the net gravitational field varies along the line AB and indicate the point where this field becomes zero.