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A train of 210 m length passes a pole in 15 seconds. Find the difference in time for the train to cross the driver and the guard of another train of length 100 m going in the same direction with a speed of 36 km/hr.1. 20 seconds2. 25 seconds3. 30 seconds4. 40 seconds5. 35 seconds |
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Answer» Correct Answer - Option 2 : 25 seconds Given: The train passes a pole in 15 seconds Length of the train = 210 m Length of second train = 100 m Speed of the second train = 36 km/hr = 10 m/sec Concept: This is a question related to relative velocity. Formula used: Relative speed in same direction = Difference in speeds between the two trains. Calculation: Speed of the first train = 210/15 = 14 m/sec Relative speed between two trains = 14 – 10 = 4 m/sec Time taken for the first train to cross the guard of the second train = 210/4 = 52.5 sec Time taken for the first train to cross the driver of the second train = (210 + 100)/4 = 77.5 sec [In order to cross the driver, the first train has to travel the combined length of both the trains] Difference in time = (77.5 – 52.5) = 25 seconds |
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