Question

State universal law of gravitation. Derive an expression for gravitational force between two bodies.

CBSE Class IX Science SA 2 (3 Marks)

Answer 1

Universal Law of Gravitation : It states that the force of attraction between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance
between them.

Let the two bodies 'A' and 'B' be of masses 'M' and 'm' respectively, which are separated by a distance According to Universal Law of Gravitation,

F oc M x m

and,                                                          F oc r²

Combining (i) and (ii), we get,

F = G M x m ²

Where, 'G' is called universal gravitation constant.

The numerical value of G = 6.67 x 10-11 Nm² kg² .

Answer 2

According to the universal law of gravitation, every particle of matter in the universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

F =G ×$\frac{m1m2}{ {r}^{2} }$