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7.Gravitation
normal
The height at which the weight of a body becomes $\frac{1}{9} ^{th}$ its weight on the surface of earth (radius of earth is $R$)
A
$h= 3\, R$
B
$h = R$
C
$h = \frac{R}{2}$
D
$h = 2R$
Solution
$g^{\prime}=\frac{g}{\left(1+\frac{h}{R}\right)^{2}}, g^{\prime}=\frac{g}{9}$
$\Rightarrow \frac{g}{9}=\frac{g}{\left(1+\frac{h}{R}\right)^{2}} \Rightarrow 1+\frac{h}{R}=3 \Rightarrow h=2 R$
Standard 11
Physics