Speed of train will help us to calculate different types of problems on motion.

1. When a train passes a stationary object:

Let x be the length of the train which includes the engine also. When the end of the train passes the object, then the engine of the train has to move a distance equal to the train.

Then the time taken by the train to pass the stationary object = length of the train/speed of the train



2. When a train passes a stationary object having some length: