How long will it take for the tail end of the 2 trains to meet each other during the course of travel

Question

2 trains, each of 120m in length, run in opposite directions with a speed of 40m/s and 20m/s. How long will it take for the tail end of the 2 trains to meet each other during the course of travel

Answer 1

Hello Roohani, 


You will first need to determine the relative speeds of both trains. 

To do so, remember: If two objects move in opposite direction at differing speeds, one speed x and another y , one simply adds both x and y to determine the relative speed. 

In your problem, one train is traveling at 40m/s and the other 20m/s. 

Therefore: 

The relative speed is 40m/s + 20m/s = 60m/s 

Next you need to determine the distance involved here: We are given two trains 120m in length, correct? 

That means the total distance is (120m + 120m) = 240m 

Finally, remember the formula for distance, time and speed? 

D = T + S   where D equals distance, T equals time and S equals speed. 

But you are looking for time, correct? 

Therefore, your formula is as follows: 

T = D/S 

The distance we discovered was 240 correct? 
The speed we discovered was 60

Therefore:

S = 240/60 

S = 4 seconds. 

I hope this helps and you have a great weekend.