Question

A 150 metres long train crosses a man walking at the speed of 6km/h in the opposite direction in 6 seconds. The speed of the train in km/h is how much?

Answer 1

Hello,

Let 'v' be the speed of the train with respect to the ground. The velocity of the man with respect to ground is -6 km/h (negative sign is included because the man and the train are moving in opposite directions). So, the velocity of the man with respect to the train is [v - (-6)] = (v + 6) km/h

Time taken by the man to cross the 0.15 Km train is = 6 s = (6/3600) h

Using, Distance = speed X time 0.15 = (v + 6) X (6/3600)

Implies, v = 84 Km/h

So, the speed of the train is 84 Km/h.