Question

Two trains, each 50 m long are travelling in opposite
direction with velocity 10 m s and 15 m s. The time
of crossing is
(a) 2 s
(b) 4 s (c) 2/3s (d) 413 s​

Answer 1

Answer:

Total lenght to cross L=50+50=100m 

relative velocity (w.r. t. other train)

v=15−(−10)=25m/s

∴t=vL=25100=4s

Explanation:

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Answer 2

Answer:

Each train's length is 50 m. Travelling in opposite direction, means the relative velocity is 10m/s + 15 m/s = 25m/s

To cross 100 m, train need

100m/(25m/sec) = 4 second

Answer is option B - 4 second