A passenger sitting in a train A moving at 90 km/h observes another train B moving in the opposite direction for 8 s. If the velocity of the train B is 54 km/h, then length of train B is: (a) 80 m (b) 200 m (c) 120 m (d) 320 m

Answer: (d). vA = 90 km/h = 25 m/s, vB = 54 km/h = 15 m/s Opposite directions: relative speed = 40 m/s Length of B = 40 × 8 = 320 m, so the answer is (d).

A passenger sitting in a train A moving at 90 km/h observes another… | JEE Main 2023 (13 Apr, Shift 2)

Q5JEE Main 2023 · 13 APR · SHIFT 2Easy

Relative Velocity

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

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Answer: (d)

$v_A = 90\text{ km/h} = 25\text{ m/s}$ , $v_B = 54\text{ km/h} = 15\text{ m/s}$
Opposite directions: relative speed $= 40\text{ m/s}$
Length of B $= 40 \times 8 = 320\text{ m}$ , so the answer is (d).

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Relative Velocity question from JEE Main 2023 (13 Apr, Shift 2)

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