Question

Two trains, each of length 100 m are travelling in opposite direction with speed 15 m/s and 25 m/s. The time taken for crossing is
1.) 4s
2.) 2.5s
3.) 5s
4.) 2s​

Answer 1

Solution -

• Two trains each of length 100m are travelling in opposite directions with speeds of 15 m/s and 25 m/s respectively.

We have to find the time taken for crossing .

Now , the two trains are moving in the opposite direction.

Total relative length = Lt1 + lt2 = 100 + 100 = 200 m .

Relative speed of the trains = | Speed 1 + Speed 2| , the modulus is bcoz the value can't be in negative. If it's in negative, it signifies the velocity is in the opposite direction .

Relative speed = | 15+25| = 40 m/s

Speed = Distance/Time

> Time = Distance/Speed = 200/40

> Time = 5s .

Answer : The time taken for crossing is 5 seconds.

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Answer 2

Given :-

Two trains, each of length 100 m are travelling in opposite direction with speed 15 m/s and 25 m/s.

To Find :-

Time taken to cross

Solution :-

We know that

Time = Distance/Speed

In this case, there are two train. So, we need to find the sum of distance and speed of both

Time = 100 + 100/15 + 25

Time = 200/40

Time = 5 s

Therefore

Time taken to cross is 5 sec