JEE Mains · Physics · STD 11 - Gravitation
- JEE Mains 2024
- Hard
- MCQ
At what distance above and below the surface of the earth a body will have same weight? (take radius of earth as \(R\).)
Pick an option to check your answer.
Answer & Solution
Correct Answer
(D) \(\frac{\sqrt{5} \mathrm{R}-\mathrm{R}}{2}\)
Step-by-step Solution
Detailed explanation
\( g_p=\frac{g R^2}{(R+h)^2} \)
\( g_q=g\left(1-\frac{h}{R}\right) \)
\( g_p=g_q \)
\( \frac{g}{\left(1+\frac{h}{R}\right)^2}=g\left(1-\frac{h}{R}\right) \)
\( \left(1-\frac{h^2}{R^2}\right)\left(1+\frac{h}{R}\right)=1\)
Take \(\frac{\mathrm{h}}{\mathrm{R}}=\mathrm{x}\)
So
\( \mathrm{x}^3-\mathrm{x}+\mathrm{x}^2=0 \)
\( \mathrm{x}=\frac{\sqrt{5}-1}{2} \)
\( \mathrm{~h}=\frac{\mathrm{R}}{2}(\sqrt{5}-1)\)
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