If a tunnel is dug by some people along the diameter of earth and then a ball is thrown through it starting from North Pole to South Pole whether it
A) stops at center
B) comes to the other pole and stop
C) goes out of tunnel.
D) it just moves up and down.
Assuming that only gravity acts on the ball, it would arrive at the South Pole with the same velocity as it had in the beginning, so if the ball was thrown, it had $v_{i} \neq 0$ which means that $v_{f} \neq 0$. So C is the correct answer.
