JEE Main · 2026 · 05 Apr 2026 · Shift 1 · Gravitation

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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

α %

. The value of

α

is ______.
(Take radius of the earth

= 6400

km.)

(A)0.12
(B)0.25✓ Correct
(C)0.50
(D)0.75

Answer: (B)

Solution

Just above the surface

g_{ab o v e} = g (1 - \frac{2 h}{R})

, and just below it

g_{b e l o w} = g (1 - \frac{h}{R})

. Moving from

16

km below to

16

km above, the magnitude of the change is

∣ g_{b e l o w} - g_{ab o v e} ∣ = g (\frac{2 h}{R} - \frac{h}{R}) = \frac{g h}{R}

. As a percentage,

\frac{g h / R}{g} \times 100 = \frac{h}{R} \times 100 = \frac{16}{6400} \times 100 = 0.25%

. Hence

α = 0.25

JEE Main · 2026 · 05 Apr 2026 · Shift 1 · Single correct option

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