Question

At a place, the value of 'g' is less by 1% than its value on the surface of the Earth (Radius of Earth, $R=6400km$). The place is :

• A. 64 km below the surface of the earth
• B. 64 km above the surface of the earth
• C. 30 km above the surface of the earth
• D. 32 km below the surface of the earth

Answer 1

Answer: (A)

64 km below the surface of the earth

Let acceleration due to gravity at a place be $g_d$. If g is acceleration due to gravity at the surface then,
$g_d=g(1-\frac{d}{R})$
$0.99g=g(1-\frac{d}{R})$
$\frac{d}{R}=\left(0.01\right)$
$d=0.01\times 6400=64km$ below the surface of earth