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JEE PHYSICS MCQ: GRAVITATION

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Application +4 | -1

A planet of mass of

\frac{1}{6}

th of earth's mass, radius of

\frac{1}{3}

rd of earth's radius. If escape speed for earth is

11.2 \mathrm{~km} / \mathrm{s}

, then escape speed for the planet shall be

\mathrm{km} / \mathrm{s}

(nearest integer).

View answer and explanation

Correct option: D

8

Option D (8) is correct because the escape speed is proportional to

\sqrt{\frac{M}{r}}

, so

v_e' = v_e \sqrt{\frac{M'}{M} \frac{r}{r'}} = 11.2 \sqrt{\frac{1/6}{1/3}} = 11.2/\sqrt{2} \approx 8 \text{ km/s}

.

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