A passenger train 60 m long travels at 80 km h⁻¹. A freight train 120 m long travels at 30 km h⁻¹. Find the ratio of the times taken by the passenger train to completely cross the freight train when (i) both move in the same direction and (ii) they move in opposite directions.
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Question

A passenger train 60 m long travels at 80 km h⁻¹. A freight train 120 m long travels at 30 km h⁻¹. Find the ratio of the times taken by the passenger train to completely cross the freight train when (i) both move in the same direction and (ii) they move in opposite directions.

Options

G1 Physics · Accepted Answer

Total relative distance in either case is 60+120=180 m. Same-direction relative speed=80-30=50 km h⁻¹. Opposite-direction relative speed=80+30=110 km h⁻¹. Since time is inversely proportional to relative speed, tsame/topposite=110/50=11/5. Hence option A.