Write Newton's universal law of gravitation and represent it in mathematical expression.

Explanation

`implies` Every body in the universe attracts every other body with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
`implies` This quotation is from Newton.s famous treatise called "Mathematical Principles of Natural Philosophy" (Principia for short).
`implies` For obtaining mathematical form of Newton.s gravitational law, let force exerted by point mass m, on the point mass `m_2 ` is  `vecF`
`:. F prop m_1m_2 " "...(1)`
`:. F prop 1/r^2" "...(2)`
`:. F prop (m_1m_2)/r^2`
`:. F = G (m_1m_2)/r^2" "...(3)`
`implies` G is called universal gravitational constant. Its value remains same in any place of universe and it is known as universal constant.
The value of G is `6.67 xx 10^(-11) (Nm^2)/(kg^2)`