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7.Gravitation
normal
Time period of simple pendulum increases by an amount $\sqrt 2 $ times at height $'h'$ from the surface of earth. Then the value of $h$ is
A
$0.25\ R$
B
$0.4\ R$
C
$0.5\ R$
D
$R$
Solution
$\mathrm{T}^{\prime}=2 \pi \sqrt{\frac{\ell}{\mathrm{g}^{\prime}}}=\sqrt{2} \cdot 2 \pi \sqrt{\frac{\ell}{\mathrm{g}}}$
$g^{\prime}=\frac{g}{2}$
$\frac{\mathrm{g} \mathrm{R}^{2}}{(\mathrm{R}+\mathrm{h})^{2}}=\frac{\mathrm{g}}{2}$
$\mathrm{h}^{2}+2 \mathrm{hR}-\mathrm{R}^{2}=0$
$\mathrm{h}=(\sqrt{2}-1) \mathrm{R}$
Standard 11
Physics