Question

A train $A$ which is $120m$ long is running with velocity $20m/s$ while train $B$ which is $130m$ long is running in opposite direction with velocity $30m/s$ . What is the time taken by train $B$ to cross the train $A$ ?

• A. $5s$
• B. $25s$
• C. $10s$
• D. $100s$

Answer 1

Answer: (A)

Length of train $A=120m$
Velocity of train $A$ , $v_A=20m/s$
Length of train $B=130m$
Velocity of train $B$ , $v_B=30m/s$
Relative velocity of $B$ w.r.t. $A=v_B+v_A=50m/s$
(trains move in opposite directions)
Total path length to be covered by $B=130+120=250m$
$\therefore$ Time taken by train $B=\frac{250m}{50m/s}=5s$