How long will a boy willing near the window of a train travelling at 36kmh^(-1) sec a train passing by in the opposite direction with a speed of 18kmh^(-1). The length of slow-moving train is 90m.

How long will a boy willing near the window of a train travelling at 3

1.	How long will a boy willing near the window of a train travelling at 36kmh^(-1) sec a train passing by in the opposite direction with a speed of 18kmh^(-1). The length of slow-moving train is 90m.
Answer» Solution :The relative velocity of the slow-moving TRAIN with respect to the boy is `=(36+18)kmh^(-1)=54xx(5)/(18)ms^(-1)=15MS^(-1)`. SINCE the boy will watch the full length of the other train, to find the TIME taken to watch full train: We have, `15=(90)/(t)ort=(90)/(15)=6s`