State the universal law of gravitation and derive its mathematical expression .

Explanation

This law states that every particle of matter in this universe attracts every other particle with a force .
This force is directly proportional to the product to the square of the distance between centers of these masses .
Let `m_1 and m_2` be the masses of two bodies A and B placed at r metre apart in space
Force `F prop m_1 xx m_2`
`F prop 1//r^(2)`
On combining the above two expressions,
`F prop ( m_1 xx m_2)/( r^(2))`
`F=(Gm_1 xx m_2)/(r^(2)) or (Gm_1m_2)/(r^(2))`
Where G is universal gravitational constant. Its value is SI unit is `6.674 xx10^(-11)N m^(2) kg^(-2)` .