Задача 40690.

Imagine a shaft penetrating the globe of one of its diameters. Find the law of motion of the body fell into the shaft, considering the changes in the gravitational acceleration inside the Earth. Friction and air resistance is ignored.

Detailed solution with the formulas and the laws used in the decision, the withdrawal of the calculation formula and the response.
If you have any questions to address, please. I´ll try to help.