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An object is kept at rest at a distance of 3R above the earth's surface where R is earth's radius. The minimum speed with whic h it must be projected so that it does not return to earth is (Assume M = mass of earth, G = Universal gravitational constant)

1. 2GM R
2. GM 2R
3. GM R
4. 3GM R

Correct answer: GM 2R

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