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7.Gravitation
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If earth has a mass nine times and radius twice to the of a planet $P$. Then $\frac{v_e}{3} \sqrt{x}\; ms ^{-1}$ will be the minimum velocity required by a rocket to pull out of gravitational force of $P$, where $v_e$ is escape velocity on earth. The value of $x$ is
A
$2$
B
$3$
C
$18$
D
$1$
(JEE MAIN-2023)
Solution
$v_{\text {(escape) plant }}=\sqrt{\frac{2 G M_P}{R_P}}$
$=\sqrt{\frac{2 G\left(\frac{M_e}{9}\right)}{\left(\frac{R_e}{2}\right)}}=\frac{v_e \sqrt{2}}{3} \therefore x=2$
Standard 11
Physics