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The value of acceleration due to gravity at Earth's surface is 9.8 ms –2 . The altitude above its surface at which the acceleration due to gravity decreases to 4.9 ms –2 , is close to : (Radius of earth = 6.4 × 10 6 m)

1. 6.4 × 10 6 m
2. 2.6 × 10 6 m
3. 1.6 × 10 6 m
4. 9.0 × 10 6 m

Correct answer: 2.6 × 10 6 m

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