Question

Find the distance (measured in earth radii, RE) from the center of the earth to a point outside the earth where the acceleration of gravity due to the earth is exactly one ninth of its value on the surface of the earth.

Answer 1

F=k/r^2 Since F is 1/9, it is apparent that r must be 3re

Answer 2

g(r) = constant *1/r^2
at r = 1 , g(1) = g
so
g(r) = g/r^2
g(r) = g/3^2 if r = 3