Answer:
The person inside the train would see the ball moving straight vertical upward and then vertically downwards also because for a person inside the train, there is only one velocity that could act on the ball and this velocity is downwards.
On the other hand, the person outside the train would see the ball appear to move along the parabolic path because the ball to this person would have two velocities acting on it: the vertical and horizontal components of velocity.
Explanation:
