As you stand beside the road singing a lovely $450\mathrm{Hz}$ note, your friend, Lisa, drives toward you at $26\mathrm{m}/\mathrm{s}$. What frequency does Lisa hear as she listens to you croon?

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency will observers hear who are located, at rest,

(b) due south, of the whistle?

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency will observers hear who are located, at rest,

(c) due east, of the whistle? and

A police siren emits a sound somewhere around 700 Hz. If you are waiting at a red light, and a police car approaches you from behind and passes you, moving at a constant 30 m/s, what is the frequency you hear from the siren as it approaches you from behind? What about once it's passed you? Assume the air temperature to be 20°C.