## Question

At what height above the earth’s surface the acceleration due to gravity will be 1/9 th of its value at the earth’s surface? Radius of earth is 6400 km.

### Solution

12800 km

If *g* be the acceleration due to gravity at the surface of the earth, then its value at a height *h* above the earth’s surface will be

or *h* = 2 *R _{e}* = 2 × 6400 = 12800 km.

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