The balloon, the light rope and the monkey shown in figure are at rest in the air. If the monkey reaches the top of the rope, by what distance does the balloon descend? Mass of the balloon $= M$ , mass of the monkey $= m$ and the length of the rope ascended by the monkey $= L$ .

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TestHub · Accepted Answer

No external force acts on the balloon + monkey system, so the centre of mass stays fixed.

Let the balloon descend by x. Then the monkey rises $L - x$ relative to ground: $m (L - x) = M x$ .

$x = \frac{m L}{m + M}$ . Hence (B).

Physics - Center of Mass Question with Solution | TestHub

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JEE Main 2028 (Class 11)