Question

The speed of sound in steel is about 4.5 km/s. A steel rail is struck with a hammer, and an observer 0.21 km away has one ear to the rail.

(a) How much time will elapse from the time the sound is heard through the rail until the time it is heard through the air? Assume that the air temperature is 20°C and that no wind is blowing. s

(b) How much time would elapse if the wind were blowing toward the observer at 23 km/h from where the rail was struck? s

Answer 1

a).The speed of sound in air at 20⁰ C is 343m/sec.

Hence time taken by the sound to reach the observer in air =

Hence time taken by the sound to reach the observer in steel =

Hence time gap = 0.612-0.046 = 0.566 sec.

b).Since wind is blowing towards obeserver,

then new speed of sound through air is = 343+6.38 = 349.38 m/sec. (as 23km/hr= 6.38 m/sesc)

Hence

Hence time taken by the sound to reach the observer in air

Hence time gap = 0.601-0.046 = 0.555 sec.