Gravitation Ques 6

6. Two spherical bodies of mass $M$ and $5 $ $M$ and radii $R$ and $2$ $ R$ released in free space with initial separation between their centres equal to $12$ $R$. If they attract each other due to gravitational force only, then the distance covered by the smaller body before collision is

[2015]

(a) $4.5 R$

(b) $7.5 R$

(c) $1.5 R$

(d) $2.5 R$

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Answer:

Correct Answer: 6.(b)

Solution:

  1. (b) Let the distance moved by spherical body of mass M is $x_1$ and by spherical body of mass $5$ $ m$ is $x_2$

Before collision At the time of collision

As their C.M. will remain stationary

So, $(M)(x_1)=(5 M)(x_2)$ or, $x_1=5 x_2$

$x_1+x_2=9$ $ R$

So, $x_1=7.5 $ $R$