A locomotive running at 54 km/h takes 20 seconds to completely cross a platform. If it takes 8 seconds to pass a standing point observer, find the platform length. MCQ with Answer and Explanation
A locomotive running at 54 km/h takes 20 seconds to completely cross a platform. If it takes 8 seconds to pass a standing point observer, find the platform length.
A. 180 meters
B. 220 meters
C. 160 meters
D. 200 meters
Answer: Option A
Solution (By JKSSB Mock Tests)
Speed of train = 54 * (5/18) = 15 m/s. Length of train = Speed * Time to cross observer = 15 * 8 = 120 meters. Total distance to cross platform = Speed * Time = 15 * 20 = 300 meters. Platform length = 300 - 120 = 180 meters.
A train leaves a station at 4:00 PM and travels at an average speed of 60 km/h. Another train leaves the same station at 5:00 PM in the same direction at an average speed of 80 km/h. At what time will the second train catch up with the first train?
Explanation:
By 5:00 PM, the first train has traveled for 1 hour and covered 60 km. Relative speed = 80 - 60 = 20 km/h. Time needed to catch up = 60 / 20 = 3 hours. Catch up time = 5:00 PM + 3 hours = 8:00 PM.
Explanation:
When A covers 100m, B covers 80m. When B covers 100m, C covers 90m. Thus, when B covers 80m, C covers 90 * (80 / 100) = 72m. Therefore, when A covers 100m, C covers 72m. A beats C by 100 - 72 = 28 meters.
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