Question

The depth at which the value of $g$ becomes $25$% of that at the surface of the earth is (in Km)

• A. 4800
• B. 2400
• C. 3600
• D. 1200

Answer 1

The correct option is A 4800

Given that $g_d=0.25g$

We have, $g_d=g(1-\frac{d}{R})$

$\therefore 0.25g=g\left(1-\dfrac d{R}\right)$

$⟹d=0.75R$

$⟹0.75\times 6400$

$⟹4800km$