Question

Two trains of equal length, running with the speeds of 60 and 40 kmph, take 50 seconds to cross each other while they are running in the same direction. What time will they take to cross each other if they are running in opposite directions?

Answer 1

Answer:

when they are moving in same direction,

then velocities should be subtracted

relative velocity=60-40=20kmph=20×5/18=50/9 mps then distance is 50/9×5 = 250/9 m

the distance covered is same in second case also so,

distance is 250/9

relative velocity in second case is =60+40=100kmph

=100×5/9 =250/9 mps

time taken to cross=distance/relative velocity

=1sec

Answer 2

Answer:

10 s

Explanation:

Formula: Distance = Speed x Time

Speed Difference = 20 km/h = 20 * (5/18) = 50 / 9 m/s

Distance = 50/9 * 50 = 2500/9 m

Total Speed = (60 + 40) = 100km/h = 100 * (5/18)

                                                          = 250/9 m/s

Time = Distance / Speed

        = (2500/9) / (250/9)

        = 10 s