Q65 / 90 · JEE Main 2023 (13 Apr Shift 2) · Physics

A passenger sitting in a train A moving at $90 km h^{- 1}$ observes another train B moving in the opposite direction for $8 s$ . If the velocity of the train B is $54 km h^{- 1}$ , then length of train B is:

A
$120 m$
Correct answer
B
$320 m$
C
$80 m$
D
$200 m$

Solution

Let the velocity of A be $v_{A}$ and the velocity of B be $v_{B}$ .
The relative velocity is
${\vec{v}}_{B A} = {\vec{v}}_{B} - {\vec{v}}_{A} \Rightarrow v_{B A} = 54 - (- 90) = 144 km h^{- 1}$
$\Rightarrow v_{B A} = 40 m s^{- 1}$
$Time = \frac{length}{v_{B A}}$
$\Rightarrow length = 40 m s^{- 1} \times 8 s = 320 m$

Hence, the correct answer is option: 'B'.

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A passenger sitting in a train A moving at 90 km h-1 observes another train B moving in the opposite direction for 8 s. If the velocity of the train B is 54 km h-1, then length of train B is:

Solution

Relevant Questions

A passenger sitting in a train A moving at $90 km h^{- 1}$ observes another train B moving in the opposite direction for $8 s$ . If the velocity of the train B is $54 km h^{- 1}$ , then length of train B is: