An untethered(free) weather balloon travelling with the wind (at wind speed) emits a 1 khz sound wave. The wind is blowing with respect to the land due east at .25 times the speed of sound in air. If the free balloon is moving away (due east)from a tower at same height, what is the frequency of the sound detected at the tower? Take the speed of sound to be 340 m/s.
Hints- draw a picture. what is the preferred reference frame?
A droppler question calculates the frequency of sound waves.