Gravitation

Acceleration due to gravity decreases as we go up or down from earth's surface.

Acceleration due to gravity is same at a height 'h' and depth 'd' from earth's surface, if $h = d$.

Acceleration due to gravity at 640 km above the earth surface decreases by 10% of its value at earth's surface (earth's radius is 6400 km)

There is reduction in acceleration due to gravity at poles due to rotation of earth as the poles are lying on the axis of rotation and do not revolve.