Question

Two identical trains take 3 sec to pass one another when going in the opposite direction but only 2.5 sec if the speed of one is increased by 50%. Find the time one would take to pass the other when going in the same direction at their original sped.

Answer 1

2s – Lenght of two train
Identical trains take 3 sec to pass one another when going in the opposite direction
2s/(v1+v2)=3
if the speed of one is increased by 50%
2s/(1.5*v1+v2)=2.5
the time one would take to pass the other when going in the same direction at their original speed.
T=2s/(v2-v1)
Having solved the system of equations, we obtain
T=15 sec