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The approximate height from the surface of the earth at which the weight of a body becomes 1/3 of its weight on the surface of the earth is (radius of the earth R=6400 km and √3=1.732)

Asked in JEE Main 24th June 1st Shift 2022 · Variation with height

Answer: (2) 4685 km

Step-by-step solution

Weight at a height obeys (W')/W=(R/(R+h))².

Setting this equal to 1/3 gives (R+h)/R=√3.

So h=R(√3-1)=6400×0.732.

h≈4685 km.

Why the other options are wrong

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