State Newton's universal law of gravitation. Hence define universal gravitational constant. Give the value of G.
Newton's universal law of gravitation
The gravitational law states that 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.
The direction of the force is along the line joining the centres of two bodies.
Fig. Law of gravitation.
As shown in Fig. above, consider two bodies A and B of masses m1 and m2.
Let r be the distance between their centres.
If F is the force with which the two bodies attract each other, then according to the law of gravitation,
Combining the two factors, we get
where G is a proportionality constant, called universal gravitational constant.
The value of G is 6.754×10−11 m3 kg−1 s−2.
