Q. If the radius of the earth were to shrink by two percent, its mass remaining the same, the acceleration due to gravity on the earth’s surface would

A) Decrease by 2%
B) Increase by 2%
C) Increase by 4%
D) Decrease by 4%
Explanation

(c) $g = \frac{GM}{R^{2}}$; If $R$ decreases then $g$ increases. Taking logarithm of both the sides;
$\log g = \log{G + \log{M = - 2\log R}}$
Differentiating it we get; $\frac{dg}{g} = 0 + 0 - \frac{2dR}{R}$
$= - 2\left( \frac{- 2}{100} \right) = \frac{4}{100}$
$\therefore\%$ increase in $g = \frac{dg}{g} \times 100 = \frac{4}{100} \times 100 = 4\%$

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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