The acceleration of gravity is inversely proportional to
the square of the distance from Earth's center.
The acceleration of gravity is 9.8 m/s² on the Earth's surface ...
6380 km from the center.
If the acceleration of gravity at 'h' is 4.9 m/s² ... 1/2 of what it is
on the surface, then the distance from the center is
(6380 x √2) = 9,023 km (rounded) ,
and 'h' is the distance above the surface
= (9,023 - 6,380) = 2,643 km (rounded) .
