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7.Gravitation
hard
The gravitational potential at a point above the surface of earth is $-5.12 \times 10^7 \mathrm{~J} / \mathrm{kg}$ and the acceleration due to gravity at that point is $6.4 \mathrm{~m} / \mathrm{s}^2$. Assume that the mean radius of earth to be $6400 \mathrm{~km}$. The height of this point above the earth's surface is :
A
$1600 \mathrm{~km}$
B
$540 \mathrm{~km}$
C
$1200 \mathrm{~km}$
D
$1000 \mathrm{~km}$
(JEE MAIN-2024)
Solution
$ -\frac{G M_E}{R_E+h}=-5.12 \times 10^{-7} \ldots . \text { (i) } $
$ \frac{G M_E}{\left(R_E+h\right)^2}=6.4 \ldots \text { (ii) }$
By $(i)$ and $(ii)$
$\Rightarrow h=16 \times 10^5 \mathrm{~m}=1600 \mathrm{~km}$
Standard 11
Physics