Newton’s Law of Gravitation :

This law states that everybody in the universe attracts each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

The force of attraction acts along the line joining the centres of the two bodies.

If m₁ and m₂ are the two masses of two bodies separated by a distance r, the force of attraction F along the line joining the centres of the two bodies :

F \alpha (\frac{m_1 m_2}{r^2})

 F= G \frac{m_1 m_2}{r^2}

Where G is the constant of proportionality and is called Gravitational Constant.