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At a certain height h above the Earth's surface, the acceleration due to gravity falls to 6.25% of its value at the surface. Find the ratio h/R, where R is the radius of the Earth.

1. 3
2. 2
3. 4
4. 1

Correct answer: 3

Solution

Use the inverse-square dependence of g with distance from Earth's centre, set it to 1/16 of surface value, and solve for h/R.

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