If I make a tunnel in the earth through its center from one place to the antipode place and throw a ball into the hole, what will happen? So far I can think, the ball will oscillate with SHM motion Making such a tunnel is not possible. I have just assumed it.
First of all a ball thrown inside a tunnel would never make it out of the other side as due to the rotation of the earth the ball would just bang into the wall.
This has been observed in deep mines.
Second, if we assume the tunnel to be from one side of earth to the other side completely coinciding with the axis of rotation (so it doesn't bang on the wall) assuming no friction then the ball would just come up the other side with same velocity you threw it in.
Third, if friction is present then it would perform oscillatory motion.(SHM with damping)