A passenger in train A moving at 90 km h⁻¹ observes train B moving in the opposite direction for 8 s. If train B moves at 54 km h⁻¹, the length of train B is:
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Question

A passenger in train A moving at 90 km h⁻¹ observes train B moving in the opposite direction for 8 s. If train B moves at 54 km h⁻¹, the length of train B is:

G1 Physics · Accepted Answer

Convert speeds: vₐ = 90/3.6 = 25 m s⁻¹ vʙ = 54/3.6 = 15 m s⁻¹ Since the trains move in opposite directions, relative speed is vᵣ = 25 + 15 = 40 m s⁻¹ Length of train B: L = vᵣt = 40 × 8 = 320 m Hence option C follows.