Here we will learn about the concept of two trains passes in the same direction.
When two train passes a moving object (having some length) in the same direction.
Let length of faster train be l meters and length of slower train be m meters
Speed of faster train be x km/hr and speed of slower train be y km/hr
Relative speed = (x – y) km/hr
Then, time taken by the faster train to pass the slower train = (l + m) meters/(x – y) km/hr
Note: Change km/hr to m/sec
Now we will learn to calculate when two trains running on parallel tracks (having some length) in the same direction.
Solved examples when two trains passes (having some length) in the same direction:
1. Two trains 130 m and 140 m long are running on parallel tracks in the same direction with a speed of 68 km/hr and 50 km/hr. How long will it take to clear off each other from the moment they meet?
Relative speed of trains = (68 – 50) km/hr
= 18 km/hr
= 18 × 5/18 m/sec
= 5 m/sec
Time taken by the train to clear off each other = sum of length of trains/relative speed of trains
= (130 + 140)/5 sec
= 270/5 sec
= 54 sec
2. The two trains are running on parallel tracks in the same direction at 70 km/hr and 50 km/hr respectively. The faster train passes a man 27 second faster than the slower train. Find the length of the faster train.
Relative speed of the trains = (70 – 50) km/hr
= 20 km/hr
= 20 × 5/18 m/sec
= 50/9 m/sec
Length of the faster train = relative speed × time taken by train to pass
= 50/9 × 27 m
` = 150 m