Q 11-07-040JEE MainJEE Main 2026 (5 Apr, Shift 1)Medium
When one moves from a point $16$ km below the earth's surface to a point $16$ km above the earth's surface. The change in g is approximately $\alpha\%$. The value of $\alpha$ is ______.
(Take radius of the earth $= 6400$ km.)
Answer: (B) $0.25$
Depth $d$: $g_d = g\left(1 - \dfrac{d}{R}\right) = g(1 - 0.0025)$.
Height $h \ll R$: $g_h \approx g\left(1 - \dfrac{2h}{R}\right) = g(1 - 0.005)$.
Change $= g(0.0025)$, i.e. about $0.25\%$ of $g$.
Solution by Sreeraj P, M.Sc Physics