If a tunnel is dug along a diameter of the Earth, and a ball is dropped in the tunnel from a certain height $h$ above the surface of Earth, what should the motion of the ball be as seen from the Earth?
The answer says it'll be along a straight line and periodic, but not simple harmonic. I understand the former. But why will it not be simple harmonic?
From what I could make out, the mean position would be the center of the Earth, with the force of gravity acting on the ball. Speed would be maximum at the mean point (center of the Earth), and minimum at the extreme positions (surface of the Earth).