Chapter 9

NCERT
Class 9
Science
Solutions
6. What happens to the force between two objects, if (i) The mass of one object is doubled. (ii) The distance between the objects is doubled and tripled. (iii) The masses of both objects are doubled.

Question:

What happens to the force between two objects, if

(i) The mass of one object is doubled.

(ii) The distance between the objects is doubled and tripled.

(iii) The masses of both objects are doubled.

Answer:

We know that, the gravitational force

F = G. m1m2/r             …(i)

(i) If the mass of one object is doubled,

then   F1 = G. (2m1)m2/r

F1 = 2. Gm1m2/r2

F1 = 2F

Therefore, the gravitational force will be two times.

(ii) If the distance between the objects is doubled.

then F2 =  G. (m1)m2/(2r)

F2 = 1/4 . Gm1m2/r2

F2 = F/4

Therefore, the gravitational force will be one-fourth.

If the distance between the objects is tripled.

then F3 =  G. (m1)m2/(3r)

F3 = 1/9 . Gm1m2/r2

F3 = F/9

Therefore, the gravitational force will be 1/9 times.

(iii) If the masses of both objects are double

 F1 = G. (2m1)(2m2)/r

F1 = 4. Gm1m2/r2

F1 = 4F

Therefore the gravitational force will be four times.

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