We know that everything that goes up comes down due to gravity .
But have you seen Moon crashing into the Earth or Earth crashing into the Sun while revolving ?
Ofcourse not .
The answer lies in the fact that they move side ways relative to the Earth's and Sun's surface .
To solve this , The Great Scientist "Issac Newton" studied the previous works of Kepler and Galileo and came up with a law for gravitation .
The Law states that :-
1) Every particle of matter attracts every other particle of matter .
2) Force of attraction is proportional to the product of masses of the particles which means heavier the bodies more the force of attraction between them .
3) If distance between the particles is doubled , the force decreases by 4 times .
Therefore , we get F∝M.m/r2
In order to turn proportionality into equation we have to replace the 'proportionality symbol' with an 'equal to' symbol and that means we have to add a constant which is 'The Universal Gravitational Constant' or G.
Therefore , F = G M.m/r2
Universal Gravitation Constant (G)
By rearranging this equation we get ,
G = Fr^2/ M.m
We can also find the SI unit of G from this equation.
Using the SI units of each of the terms used in equation we get ,
SI unit of G = N m^2/kg^2
Value of G
Henry Cavendish conducted a very complicated experiment with complicated formulas and found the value of G which is 6.67 * 10^-11
G = 6.67 * 10^-11
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