Question
Train A when travelling with a speed of 108 km/h crosses a
pole in 8 seconds. Find the time taken by the train A to cross another train B of length 50% more than that of train A which is coming from the opposite direction with a speed of 72 km/h.Solution
Speed of train A = 108 × 5/18 = 30 m/s
Length of train A = 30 × 8 = 240 metres
Length of train B = 1.5 × 240 = 360 metres
Speed of train B = 72 × 5/18 = 20 m/s
Relative speed = 30 + 20 = 50 m/s (opposite direction)
Total distance = 240 + 360 = 600 metres
Desired time = 600/50 = 12 seconds
A device used for converting A.C. into D.C. is called –
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