A train running at 54 km/h takes 20 seconds to pass a bridge. Next, it passes a man walking at 6 km/h in the same direction in 12 seconds. Find the length of the bridge. MCQ with Answer and Explanation
A train running at 54 km/h takes 20 seconds to pass a bridge. Next, it passes a man walking at 6 km/h in the same direction in 12 seconds. Find the length of the bridge.
A. 120 meters
B. 150 meters
C. 140 meters
D. 160 meters
Answer: Option C
Solution (By JKSSB Mock Tests)
Speed of train = 54 km/h = 15 m/s. Speed of man = 6 km/h = 5/3 m/s. Relative speed = 15 - 5/3 = 40/3 m/s. Length of train = Relative speed * time = (40/3) * 12 = 160 meters. To pass bridge: Total distance = Length of train + Length of bridge = 15 m/s * 20 seconds = 300 meters. Length of bridge = 300 - 160 = 140 meters.
Two locomotive train units 140 meters and 110 meters long are running along parallel track loops in identical directions at speeds of 52 km/h and 42 km/h respectively. In what timeframe will the faster train clear the slower train completely?
A thief is spotted by a policeman from a distance of 200 meters. The thief runs at 10 km/h and the policeman chases him at 12 km/h. Find the distance covered by the thief before he is caught.
Explanation:
Relative speed = 12 - 10 = 2 km/h. Time to catch the thief = 0.2 km / 2 km/h = 0.1 hours. Distance covered by thief = Speed * Time = 10 km/h * 0.1 hours = 1 km = 1000 meters.
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