Answer:
According to the gravitational law of Isaac Newton, "the gravitational force between any two objects is proportional to the product of the objects’ masses and inversely proportional to the square of the separation between their centers".
Therefore gravitational constant is the proportionality constant used in Newton’s Law of Universal Gravitation, and is commonly denoted by G. It is expressed as:
F= Gm1m2/r2
Another scientist Cavendish was able to measure the gravitational force and the value of the proportionality constant. It is expressed as G = 6.673×10-11 N m2 kg-2.