Question

Why is G called the universal gravitation constant? define it.write it's expressions value and S. I. Unit

Answer 1

the first equation above, g is referred to as the acceleration of gravity. Its value is 9.8 m/s2 on Earth. That is to say, the acceleration of gravity on the surface of the earth at sea level is 9.8 m/s2. When discussing the acceleration of gravity, it was mentioned that the value of g is dependent upon location.

Answer 2

According to Universal Law of gravitition =>

Gravitional force is directly proportional to the product of mass of two objects and inversely proportional to the square of distance between them...

=> F =( G × m1 × m2 ) / r ^2
=> G = ( F × r ^ 2 ) / ( m1 × m2 ) --- ( i )
take m1 = 1 kg and m2 = 1 kg and r = 1 meter in ( i ) then we must have , G = F
This means that G is defined as the force F experienced between the two bodies of mass 1 kg each which are kept at a distance of 1 meter from their center .

The value of G is calculated by Henry Cavendish and is numerically equal to 6.67 × 10 ^ -11 Nm^2 Kg^-2

This value of G is doesnt not change in any situation...This means that No matter you put masses of bodies in any planet or any surface or any medium ( liquid , gas , solid ) , The G remain constant..
.This is also applicable in universe too..So called Universal Gravitional Constant...

SI unit of G is N m^2 kg^-2 ( Newton MeterSquared Kilogram raised to the power minus 2 ).