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If you stand on a tall ladder so that your distance from the Earth's centre becomes $2R$, your weight becomes what fraction of its value on the surface?
ATwice
BOne-half
COne-fourth
DOne-eighth
Answer & Solution
Correct answer: C. One-fourth
1. Weight $W = mg = \dfrac{GMm}{r^2}$, so $W \propto \dfrac{1}{r^2}$ for fixed mass.
2. At the surface $r = R$; on the ladder $r = 2R$.
3. The ratio $\dfrac{W_{2R}}{W_R} = \dfrac{R^2}{(2R)^2} = \dfrac{1}{4}$.
4. So weight falls to one-fourth; 'one-half' wrongly assumes $W \propto 1/r$ and is the trap.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 1 "Gravitation", p.19_
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