The height at which the acceleration due to gravity becomes g/9 (where g = the acceleration due to gravity on the surface of the earth) in terms of R, the radius of the earth, is

  1. (√2)R
  2. R/2
  3. R/√2
  4. 2R


GM/(9R2) = GM/(R + h)2

3R = R + h

h = 2R

The correct option is D.