A boy sitting in a train which is travelling at 60 km/hr observes that a goods train, travelling in opposite direction, takes 6 seconds to pass him. If the goods train is 220 m long, find its speed.
Relative speed = (220/6) m/sec. = (220/6 * 18/5) km/hr = 132 km/hr.
.'. Speed of goods train = (132 - 60) = 72 km/hr.
( '.' Suppose two trains or two bodies are moving in the opposite direction at u m/s and v m/s,
then their relative speed = (u + v) m/s. )
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