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It is possible to detect a distant train, which still can't be heard, approaching us by placing our ear very near to the railway line. How this works ?

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### Step-by-Step Solution: 1. **Understanding Sound Propagation**: - Sound travels through different mediums at different speeds. In air, the speed of sound is approximately 330 meters per second (m/s), while in solids (like a railway line), it can be around 1500 meters per second (m/s). 2. **Distance Calculation**: - If a train is 1 kilometer (1000 meters) away, the time it takes for the sound to reach us through air can be calculated using the formula: \[ ...
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How is it possible to detect the approaching of a distant train by placing the ear very close to the railway line ?

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