Important Rule On Train Problems
1. Converting km/hr into m/sec a km / hr = (a x 5/18) m / sec
2. Converting m / sec into km/hr b m / sec = (a x 18/5) km/ hr
3. Time taken by a train of length l meters to pass a pole or a standing man or a signal post is equal to the time taken by the train to cover l meters.
4.Time taken by a train of length l meters to pass a stationary object of length b meters is the time taken by the train to cover(l + b) meters.
5.Suppose two trains or two bodies are moving in the same direction at u m / sec and v m / sec, where
u>v , then their relative speed is = (u - v) m / sec.
6.Suppose two trains or two bodies are moving in opposite directions at u m / sec and v m / sec, then relative speed is = (u + v) m / sec.
7. if two trains of length a meters and b meters are moving in opposite directions at u m / sec and v m / sec, then time taken by the trains to cross each other = (a + b) / (u + v) sec.
8. if two trains of length a meters and b meters are moving in the same direction at u m / sec and v m / sec then the time taken by the faster train to cross the slower train = ( a + b ) / ( u - v ) sec.
9.if two trains start at the same time from ponts A and B towards each other and after crossing they take a and b sec in reaching B and A respectively then (A' s speed) : (B ' s speed) = (√b : √a).
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