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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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બે ટ્રેન A અને B અનુક્રમે 66 કિમી/કલાક અને 60 કિમી/કલાકની ઝડપે વિરુદ્ધ દિશામાં ચાલી રહી છે. જો ટ્રેન A ની લંબાઈ 240 મી હોય અને તેઓ એકબીજાને 10 સેકન્ડમાં પાર કરે, તો ટ્રેન B ની લંબાઈ શોધો.
110 મી
120 મી
150 મી
144 મી
110 મી
Convert relative speed to m/s by multiplying with 5/18. Total distance = Relative speed × time. Then subtract length of train A from total distance.
Speed of train A = 66 km/hr, Speed of train B = 60 km/hr, Length of train A = 240 m, Crossing time = 10 s
Speed=TimeDistance,Relative Speed=S1+S2(opposite directions)
Convert relative speed to m/s by multiplying with 5/18. Total distance = Relative speed × time. Then subtract length of train A from total distance.
Forgetting to convert km/hr to m/s before multiplying by time in seconds, or failing to add speeds for opposite directions.
Calculate Relative Speed
Since the trains are running in opposite directions, their speeds are added.
Relative Speed=66+60=126 km/hr
Convert Speed to m/s
To match the units of length (m) and time (s), convert 126 km/hr to m/s.
126×185=7×5=35 m/s
Calculate Total Distance
Total distance is the sum of lengths of both trains.
Distance=Speed×Time=35×10=350 m
Find Length of Train B
Subtract the length of train A from total distance to find the length of train B.
LB=350−240=110 m
A is correct because the calculated length of train B is 110 m.
This concept is vital for Boat and Stream problems where effective speed changes based on direction (upstream/downstream).