A 220 metre long train is running at a speed of 54 kilometre per hour. In what time will it pass a man who is moving in the opposite direction of the train at speed of 12 kilometre per hour?

Concept:

When two bodies run in the opposite direction, then their relative velocities get added.

1 km/hr = 5/18 m/s.

1 m/s = 18/5 km/hr.

Calculation:

Length of train = 220 m, Speed of train = 54 km/hr ⇒ 15 m/s and Speed of man = 12 km/hr ⇒ 10/3 m/s [ 1 km/hr = 5/18 m/s]

\(Time = \frac{Distance}{Speed}\)

⇒ \(\frac{220}{\frac{10}{3}\;+\;15} \)   -----(Speed gets added due to different direction)

\(⇒ \frac{220\;\times\;3}{55}\)

⇒ 12 sec.