Answer:
The gravitational potential energy of the sphere would be reduced to [tex](1/2)[/tex] of the initial value.
Explanation:
Near the surface of the Earth, the gravitational field is approximately uniform. The gravitational field strength is approximately [tex]g \approx 9.81\; {\rm N \cdot kg^{-1}}[/tex].
In a uniform gravitational field, the gravitational potential energy (GPE) of an object relative to the ground is proportional to height. For example, if an object of mass [tex]m[/tex] is at a height [tex]h[/tex] above the ground, the GPE of this object would be [tex]m\, g\, h[/tex] relative to the ground.
In this example, the height of the sphere is reduced to [tex](1/2)[/tex] of its initial value. As a result, the GPE of this sphere relative to the ground would also be reduced to [tex](1/2)\![/tex] of the initial value.
