distance to overtake trailer:
4+20m=24m
convert speed km/hr to m/s:
36/1*1/60min*1/60sec*1000m/1=36000/3600=10m/s
relative rates same direction (subtract):
distance/(r1-r2)=10secs
24/x-10=10, 24=10x-100, x=124/10=12.4m/s
OR
To pass the truck, the car must cover its own length of 4 meters and the truck’s length of 20 meters —— in other words, the Car must close a “Gap Distance” = (4 + 20) = 24 met
The truck travels at 36 km per hour
1 km = 1,000 meters
1 hour = 3,600 seconds
Truck travels at Speed = 36, 000 meters / 3, 600 seconds = 10 meters/seconds
Let the Speed of Car = C meters / second
Since the Car and Truck are traveling in the SAME Direction, for every meter the car tries to close the “Gap Distance” it is being hindered by the Speed of the Truck
Relative Speed = (C - 10) met/sec
Time for the car to cross the truck :
Time = Gap Distance / Relative Speed
Time = 10 sec = 24 met / (C - 10) met/ sec
10C - 100 = 24
10C = 124
C = 12.4 meters/second
Answer C
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