Question

Passenger A sits inside a moving train and throws a ball vertically upward. How would the motion of the ball be described by a fellow train passenger B and an observer C who is standing on the platform outside the train?

a) Passenger B sees the ball moving forward, and observer C sees it moving backward
b) Passenger B sees the ball moving upward, and observer C sees it moving downward
c) Passenger B sees the ball moving upward, and observer C sees it moving forward
d) Passenger B sees the ball moving forward, and observer C sees it moving upward

Answer 1

Passenger B on the moving train would see the ball move straight up and down while observer C on the platform would see the ball follow a parabolic path with both vertical and horizontal components, exemplifying relative velocity.

Step-by-step explanation:

When Passenger A inside a moving train throws a ball vertically upward, the motion perceived by the observers depends on their frames of reference. Passenger B, who is on the train, would see the ball move straight up and then down because they share the same horizontal motion as the train. Conversely, observer C, standing on the platform, would observe the ball following a parabolic path, moving both vertically and horizontally. This difference is due to the fact that observer C sees the ball retaining the horizontal motion of the train in addition to its own vertical motion, illustrating the concept of relative velocity.

Applying this understanding to the GRASP CHECK and the provided options:
a. Passenger B would see the ball with vertical, but no horizontal, motion.
c. Observer C would see the ball with vertical as well as horizontal motion.

The correct answer to the question is therefore: a) Passenger B sees that the ball has vertical, but no horizontal, motion. Observer C sees the ball has vertical as well as horizontal motion.