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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Train A is 260 m long and crosses a platform of length 160 m in 28 seconds. Train B is 340 m long and passes a stationary man in 20 seconds. Both trains travel at constant speeds on parallel straight tracks. Find the time (in seconds) taken when the faster train completely overtakes the slower train while moving in the same direction?
250
320
360
300
300
Calculate speeds separately: SA=(260+160)/28=15 m/s, SB=340/20=17 m/s. Relative speed = 17−15=2 m/s. Time = sum of lengths / relative speed = (260+340)/2=300 seconds.
Train A: length = 260 m, crossing 160 m platform in 28 s. Train B: length = 340 m, crossing a man in 20 s.
Speed=TimeDistance, Relative Speed=SB−SA, Time=Relative SpeedTotal Length
Calculate speeds separately: SA=(260+160)/28=15 m/s, SB=340/20=17 m/s. Relative speed = 17−15=2 m/s. Time = sum of lengths / relative speed = (260+340)/2=300 seconds.
Students often add the lengths of both trains when crossing a man or a platform, but you must only add the lengths of the two trains when they are overtaking each other.
Calculate speed of Train A
Train A covers its own length plus the platform length. Total distance = 260+160=420 m. SA=420/28=15 m/s.
SA=28260+160=15 m/s
Calculate speed of Train B
Train B crosses a stationary man, so it covers only its own length. SB=340/20=17 m/s.
SB=20340=17 m/s
Calculate relative speed and time to overtake
Since trains move in the same direction, relative speed is the difference of speeds. Total distance to cover is the sum of both train lengths: 260+340=600 m.
Time=17−15260+340=2600=300 s
D is correct because the faster train (Train B) overtakes Train A in 300 seconds.
This concept is fundamentally identical to circular track problems where the faster runner laps the slower runner by the circumference of the track.