Q. The height from the earth surface at which the value of acceleration due to gravity reduces to $1/4^{th}$ of its value at earth’s surface (assume earth to be sphere of radius $6400\ km$)

A) $6400\ km$
B) $2649\ km$
C) $2946\ km$
D) $1600\ km$
Explanation

(a) $g^{'} = \frac{g}{\left( 1 + \frac{h}{R} \right)^{2}}$
$\frac{g}{4} = \frac{g}{\left( 1 + \frac{h}{R} \right)^{2}}$
$1 + \frac{h}{R} = 2 \Rightarrow \frac{h}{R} = 1$
$\Rightarrow h = R$
$\therefore h = 6400km$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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