The relative motion of the train next to her is the motion of the other train in her rest frame.
As the other train leaves, it seems to Sunita as if her train is moving backwards
Reason:
The motion of the train Sunita is taking is given by the rate of movement of
objects outside the train from the front side of the train towards the back
side of the train, that way she can tell that the train is moving.
The motion of the other train from the rear side of the train from the rear
side of the train to the front side is a reverse motion to what Sunita
observes when the train is moving forward. Therefore, as the other train
leaves, it seems to Sunita as if her train is moving backwards.
Learn more here:
https://brainly.com/question/25100629
