Question

Two trains each of length 100 m are running on parallel tracks. One overtakes the other in 20 s when they are moving in the same direction and crosses the other in 10s when they move in the opposite directions. The velocities of the two trains are
(1) 15 m/s & 5 m/s (2) 25 m/s & 15 m/s
(3) 10 m/s & 10 m/s (4) 30 m/s & 10 m/s
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Answer 1

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◆ Let u & v be the velocity of the two trains named A & B.

While overtaking the relative velocity of train A with respect to B = u - v.

While crossing, the relative velocity of train A with respect to B = u + v.

◆Total distance to be travelled by Train A while crossing = 100 + 100 = 200.

So,

20 = 200 ÷ u-v

=> u - v = 10....1)

Also,

10 = 200 ÷ u + v

=> u + v = 20.......2)

◆◆ On solving the equation 1 & 2, we get;◆◆

u = 15 M/S of the train A / First Train.

v= 5 M/S of the train B / Second Train.

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