General Formulas ( Problems on Trains)

• x km/hr = x×518 m/s 


• y m/s = y×185 km/hr 


• Speed = distance/time
  s = d/t


• velocity = displacement/time
  v = d/t


• Time taken by a train x meters long to pass a pole or standing man or a post
  = Time taken by the train to travel x meters.


• Time taken by a train x meters long to pass an object of length y meters
  = Time taken by the train to travel (x + y) metres.


• Suppose two trains or two objects are moving in the same direction at v1 m/s and v2 m/s where v1 > v2,
  then their relative speed = (v1 – v2) m/s


• Suppose two trains or two objects are moving in opposite directions at v1 m/s and v2 m/s ,
  then their relative speed = (v1+ v2) m/s


• Assume two trains of length x metres and y metres are moving in opposite directions at v1 m/s and v2 m/s, Then
  The time taken by the trains to cross each other = (x+y) / (v1+v2) seconds


• Assume two trains of length x metres and y metres are moving in the same direction at at v1 m/s and v2 m/s where v1 > v2, Then
  The time taken by the faster train to cross the slower train = (x+y) / (v1-v2) seconds


• Assume that two trains (objects) start from two points P and Q towards each other at the same time and after crossing they take p and q seconds to reach Q and P respectively. Then,
  
  
  A's speed: B's speed = q√:p√