Question

Two trains, each 50 m long are travellig in opposite directions with velocities 10 m/s and 15 m/s. The time of crossing is _____?

Answer 1

Both are moving in opposite direction so, their relative velocities of both train became 25 m/s means train velocity now taken as 25 m/s. As both train are 50 m long…they have to travel 100m to cross each other.

So by equation,

Time= distance/velocity

Time= 100/25

Answer= 4 seconds

Answer 2

Length of each train = 50 m

Effective distance which needs to be covered by each train to cross over = 50 + 50 = 100 m

velocity of first train = 10 m/s

velocity of second train = 15 m/s

net relative velocity = 15 - (-10) (as the trains are travelling in opposite directions)

= 25 m/s

time taken to travel 100 with velocity 25 m/s = 100 / 25 = 4 seconds