Question

A car is moving at a rate of 50 m/s when suddenly the driver hit the horn that emits 20000Hz frequency. What will be the perceived frequency of a man standing at the sidewalk if the speed of the sound is 340 m/s and the car is moving away from the location of the man?

Answer 1

We can find the frequency heard by the man from the Doppler Shift formula:

$$f_o=f_s(\dfrac{v}{v+v_s}),$$ $$f_o=2\cdot10^4\ Hz\cdot(\dfrac{340\ \dfrac{m}{s}}{340\ \dfrac{m}{s}+50\ \dfrac{m}{s}})=1.74\cdot10^4\ Hz.$$