TRAINS

 General Concept:-

(1) Time taken by a train x mt long in passing a signal post
 or a pole or a standing man = time taken by the train to cover x mt


(2) Time taken by a train x mt long in passing a stationary
 object of length y mt = time taken by the train to cover x+y mt


(3) Suppose two trains or two bodies are moving in the same 
direction at u kmph and v kmph such that u > v then their 
relative speed is u-v kmph


(4)If two trains of length x km and y km are moving in opposite
 diredtions at u kmph and vmph,then time taken by the train to
 cross each other = (x+y)/(u+v) hr


(5) Suppose two trains or two bdies are moving in opposite direction
 at u kmph and v kmph then,their relative speed = (u+v) kmph


(6)If two train start at the same time from 2 points A & B towards
 each other and after crossing they take a & b hours in reaching B & A respectively
          then A's speed : B's speed = (b^1/2 :   a^1/2 )
BACK