Speed

The speed of sound in air is approximately \(343\) m/s. Using this speed of sound, consider the following circumstances:

1. At an observation point, a lightning flash is seen \(5.3\) seconds before a thunder is heard. Find the distance between the observation point and where the lightning happens. You may assume that time lapse between the occurrence of the lightning flash and its detection at the observation point is negligible.
   
2. A ship whistles at some point on the sea, and two beacons, Beacon A and Beacon B, hear the whistle. Given that Beacon A hears the whistle \(2.1\) seconds after Beacon B does, and that the distance between the ship and Beacon B is \(686\) m when the ship whistles. Find the distance between the ship and Beacon A when the ship whistles.
   
3. An engine is started at some point in the middle of two mountains. After \(2.5\) seconds and \(4\) seconds respectively, two echoes are heard. Assuming the engine and the two mountains lie on the same straight line, find the horizontal distance between the two mountains.