A small point of mass is placed at a distance from the center of a big uniform solid sphere of mass and radius . The gravitational force on due to is . A spherical part of radius is removed from the big sphere as shown in the figure, and the gravitational force on due to the remaining part of is found to be . The value of the ratio is:
The height from Earth's surface at which acceleration due to gravity becomes is ? (Where is the acceleration due to gravity on the surface of the Earth and is the radius of the Earth.)