Question

A $120m$ long train is moving in a direction with speed $20m/s$. A train $B$ moving with $30m/s$ in the opposite direction and $130m$ long crosses the first train in a time of :

• A. $5s$
• B. $36s$
• C. $38s$
• D. $Noneofthese$

Answer 1

The correct option is A $5s$

Given,

$S_A=120m$

$S_B=130m$

$v_A=20m/s$

$v_B=30m/s$

The velocity of approach, $v=v_A+v_B$

$v=20+30=50m/s$

The train A has to cover the distance, $S=S_A+S_B$

$S=120+130=250m$

Time, $t=\frac{S}{v}=\frac{250}{50}$

$t=5sec$

The correct option is A.