Two friends stand 1.0km ahead of an approaching train on a straight track. Friend X places an ear on the steel rail, while friend Y stands upright beside the track. When the driver sounds the whistle, friend X hears the sound 2.5s earlier than friend Y. (Take the speed of sound in air as 340m/s.)
(a) Calculate the time taken for the whistle sound to reach friend Y through air.
(b) Using the information above, determine the speed of sound in the steel rail.
(c) At what distance ahead of the train must the friends repeat the experiment if friend X is to hear the whistle exactly 5.0s earlier than friend Y? Assume the same speeds in both media.
(d) Explain briefly, in terms of particle arrangement in solids and gases, why sound travels faster in steel than in air.