the ball straight up into the air, and then catches it again. did the speed of the train cause the ball to travel so that the boy caught the ball in a different place compared to the position from which he tossed the ball into the air? surprisingly, the answer depends upon whom you ask.
if you were to ask the boy, he would tell you no, silly, the ball went straight up and down, and it landed at the exact same spot from where he threw it. if you were to ask a farmer standing in her field beside the train tracks, she would tell you she saw the boy 