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Kinematics

JEE Main level, single correct, medium

145 of 308

Question 145 of 308

Two trains $A$ and $B$ of length $l$ and $4l$ are travelling into a tunnel of length $L$ in parallel tracks from opposite directions with velocities $108km{h}^{-1}$ and $72km{h}^{-1},$ respectively. If train $A$ take $35s$ less time than train $B$ to cross the tunnel then, length $L$ of tunnel is:
(Given $L=60l$ )

Show answer and solution

Answer: (C) $1800m$

The time taken for

A

\Delta {t}_{A}=\dfrac{l+L}{{V}_{A}}

The time taken for

B

\Delta {t}_{B}=\dfrac{4l+L}{{V}_{B}}

It is given that

B

takes more time than

A

. So,

\Rightarrow \dfrac{4l+L}{20}-\dfrac{l+L}{30}=35

\Rightarrow \dfrac{64l}{20}-\dfrac{61l}{30}=35

\Rightarrow l=\dfrac{35\times 600}{700}=30m

Therefore,

L=1800m

JEE Main question paper PDF

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JEE Main 2025 Apr 2 Shift 1 question paper

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