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.

Explanation

Acceleration due to gravity at height h is
`g'=(g)/((1+(h)/(R_(e)))=(g)/(9)implies(1+(h)/(R_(e)))=3`
`impliesh=2R_(e)=12800" km".`