A 240 meters long train running at the speed of 120 km/hr passed a 280...
Given:
Length of the train = 240 meters
Speed of the train = 120 km/hr
Length of the platform = 280 meters
Time taken to pass the platform = T seconds
Time taken to pass the tunnel = 12.6T seconds
To find:
Length of the tunnel
Approach:
First, we need to find the time taken by the train to pass the platform.
Then, we can calculate the speed of the train in meters per second.
Using the speed and time, we can calculate the distance covered by the train in passing the platform.
Finally, we can calculate the length of the tunnel by subtracting the distance covered in passing the platform from the total distance covered in passing the tunnel.
Calculations:
1. Time taken to pass the platform:
Distance = Length of the platform = 280 meters
Speed = 120 km/hr = (120 * 1000) / 3600 m/s = 100/3 m/s (converting km/hr to m/s)
Time = Distance / Speed = 280 / (100/3) = (280 * 3) / 100 = 8.4 seconds
2. Speed of the train in meters per second:
Speed = 120 km/hr = (120 * 1000) / 3600 m/s = 100/3 m/s
3. Distance covered in passing the platform:
Distance = Length of the train + Length of the platform = 240 + 280 = 520 meters
4. Time taken to pass the tunnel:
Time = 12.6T seconds
5. Total distance covered in passing the tunnel:
Distance = Length of the train + Length of the tunnel
Using the above calculations, we can write the equation:
Distance = Speed * Time
240 + Length of the tunnel = (100/3) * (12.6T)
240 + Length of the tunnel = (42/10) * (126T)
240 + Length of the tunnel = 42 * 12.6T
Length of the tunnel = (42 * 12.6T) - 240
Length of the tunnel = 529.2T - 240
Substituting the value of T = 8.4, we get:
Length of the tunnel = (529.2 * 8.4) - 240
Length of the tunnel = 4444.08 - 240
Length of the tunnel = 4204.08 meters
Therefore, the length of the tunnel is approximately 4204.08 meters.
The correct answer is option D) 700 meters.