Question

how long will a boy sitting near the window of a train travelling at 54 km/hr see a train passing by in the opposite direction with a speed of 36 km/hr. the length of the slow-moving train is 100m

Answer 1

The speeds should first be converted to meters per second.

54 × 5/18 = 15m/s

36 × 5/18 = 10m/s

The relative speed of two approaching bodies is the sum of the two speeds.

In this case we have :

Relative speed :

15 + 10 = 25m/s

Relative distance is 100 m

Time = Distance /speed

100/25 = 4 seconds

Time is therefore 4 seconds