If a satellite orbiting the Earth is 9 times closer to the Earth than the Moon, what is the time period of…

If a satellite orbiting the Earth is 9 times closer to the Earth than the Moon, what is the time period of rotation of the satellite? Given rotational time period of Moon $=27$ days and gravitational attraction between the satellite and the moon is neglected.
  1. 27 days
  2. 1 day
  3. 81 days
  4. 3 days

Solution

$\begin{aligned} & \mathrm{T}^2 \propto \mathrm{R}^3 \\ & \left(\frac{\mathrm{~T}_{\mathrm{m}}}{\mathrm{T}_{\mathrm{s}}}\right)^2=\left(\frac{\mathrm{R}}{\mathrm{R} / 9}\right)^3 \\ & \frac{\mathrm{~T}_{\mathrm{m}}}{\mathrm{T}_{\mathrm{s}}}=(3)^3 \\ & \Rightarrow \mathrm{~T}_{\mathrm{s}}=\left(\frac{27}{27}\right)=1 \text { day }\end{aligned}$

Asked in: JEE Main 2025 (23 Jan Shift 2)

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