Two trains of length 120 meter and 150 meter crosses a stationary man ...
120 = a*10, a = 12 m/sec (speed of first train)
150 = b*15, b = 10 m/sec (speed of second train)
270 = (2)*T, T = 135 seconds
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Two trains of length 120 meter and 150 meter crosses a stationary man ...
Problem:
Two trains of length 120m and 150m crosses a stationary man in 10s and 15s respectively. In what time they will cross each other when they are moving in the same direction.
Solution:
Let the speed of the first train be x m/s and that of the second train be y m/s.
When the trains are moving in the same direction, the relative speed of the second train with respect to the first train is (y - x) m/s.
Time taken by the first train to cross the man = Length of the first train / Relative speed
So, we have
120 / x = 10
=> x = 12 m/s
Time taken by the second train to cross the man = Length of the second train / Relative speed
So, we have
150 / (y - x) = 15
=> y - x = 10 m/s
Now, the distance between the two trains when the first train completely crosses the man = Length of the first train + Length of the man = 120 + 0 (since the man is stationary) = 120m
Relative speed of the two trains when they are moving in the same direction = (y - x) m/s = 10 m/s
Time taken by the two trains to cross each other = Distance between the two trains / Relative speed
So, we have
(120 + 150) / 10 = 27s
Therefore, the correct answer is option C, i.e. 135s.
Two trains of length 120 meter and 150 meter crosses a stationary man ...
Solved :-
we solve this question by relative motion . we will have to at first calculated speed of both train that is 10m/s and 12m/s respectively.
Now question is that find out how much time taken by them for crosses each other?
Then I applying relative motion between them that is for calculation relative motion, I will have to speed of anyone train in both is stationary w. r. t other train that is zero (0).
Here I am considering first train is in stationary stage w. r. t other , then speed of second train w. r. t first train (12-10) =2m/s.
Now according to the question for crosses to each other, Second train will have to covered total length of train A and train B ( because train A is stationary) = 150m+120m =>270m.
Time taken by train B for crosses train A=
( total distance covered by B / relative speed of train B w. r. t A)
= 270m / 2m/s =>135s
Now option C i.e 135sec is correct option.
That solved