What is the importance of universal law of gravitation?

 As the altitude of the body increases do the weight and mass both vary?

 Can a body have weight but no mass?

What is the significance of each symbol in the equation? h = ut + 1/2 gt².

What is meant by free fall of a body?

The force of gravitation between two objects of masses $50 \mathrm{kg}$ and $120 \mathrm{kg}$ respectively kept at a distance of $10 \mathrm{m}$ from one another is $4.02\times {10}^{-n} \mathrm{N}$. Find the value of $n$. 
(Gravitational constant, $G = 6.7\times {10}^{-11} {\mathrm{Nm}}^2/{\mathrm{kg}}^2$)