UNIVERSAL LAW OF GRAVITATION
Every object in the universe attracts every other object with a force . Attraction force is directly proportional to the product of their masses.
F ∝ m1 × m2 Equation 1
The force between two objects is inversely proportional to the square of the distance between them, that is,
F ∝ 1/ r2 Equation 2
Combining Eqs. (1) and (2), we get
F ∝ m1 m2 / r2 Equation 3
F = G m1 m2 / r2 Equation 4
where G is the constant of proportionality and is called the universal gravitation constant.
m1 = Mass of one body
m2 = Mass of other body
r = Distance between two body
By multiplying crosswise, Eq. (4) gives
F × r 2 = G m1 × m2
G = F × r 2 / m1 × m2 Equation 5
IMPORTANCE OF THE UNIVERSAL LAW OF GRAVITATION
The universal law of gravitation successfully explained several phenomena which were believed to be unconnected:
(i) the force that binds us to the earth;
(ii) the motion of the moon around the earth;
(iii) the motion of planets around the Sun; and
(iv) the tides due to the moon and the Sun.