The ratio of energy required to raise a satellite of mass ' $\mathrm{m}$ ' to height ' $h$ ' above the…

The ratio of energy required to raise a satellite of mass ' $\mathrm{m}$ ' to height ' $h$ ' above the earth's surface to that required to put it into the orbit at same height is [ $\mathrm{R}=$ radius of earth $]$
  1. $\frac{\mathrm{h}}{\mathrm{R}}$
  2. $\frac{2 \mathrm{~h}}{\mathrm{R}^2}$
  3. $\frac{3 \mathrm{~h}}{\mathrm{R}^2}$
  4. $\frac{2 h}{R}$

Solution

Energy required to raise to satellite of $m$ to a height $h$ is equal to change in its potential energy. $\therefore \mathrm{W}=-\frac{\mathrm{GMm}}{\mathrm{R}+\mathrm{h}}+\frac{\mathrm{GMm}}{\mathrm{R}}=\frac{\mathrm{GMmh}}{(\mathrm{R}+\mathrm{h}) \mathrm{R}}$ The energy of a satellite moving in a circular orbit is given by $\begin{aligned} & \mathrm{E}=\frac{\mathrm{GMm}}{2(\mathrm{R}+\mathrm{h})} \\ & \therefore \frac{\mathrm{W}}{\mathrm{E}}=\frac{2 \mathrm{~h}}{\mathrm{R}} \end{aligned}$

Asked in: MHT CET 2021 (21 Sep Shift 2)

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