The radius of the orbit of a geostationary satellite is (mean radius of the earth is $\mathrm{R}$, angular…

The radius of the orbit of a geostationary satellite is (mean radius of the earth is $\mathrm{R}$, angular velocity about an axis in $\omega$ and accleration due to gravity on earth's surface is g)
  1. $\left(\frac{g R^{2}}{\omega^{2}}\right)^{1 / 3}$
  2. $\frac{g R^{2}}{\omega^{2}}$
  3. $\left(\frac{g R^{2}}{\omega^{2}}\right)^{2 / 3}$
  4. $\left(\frac{g R^{2}}{\omega^{2}}\right)^{1 / 2}$

Solution

$\begin{aligned} m r \omega^{2} &=\frac{G M m}{r^{2}} \\ r \omega^{2} &=\frac{G M}{r^{2}} \\ r^{3} &=\frac{G M}{\omega^{2}}=\frac{G M}{R^{2}} \times \frac{R^{2}}{\omega^{2}}=g \frac{R^{2}}{\omega^{2}} \\ r &=\left(\frac{R^{2} g}{\omega^{2}}\right)^{1 / 3} \end{aligned}$

Asked in: MHT CET 2020 (14 Oct Shift 2)

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