A car horn emits a frequency of 400 Hz.A car traveling at 30.0 m/s sounds the horn as it approaches a stationary pedestrian.What frequency does the pedestrian hear? The speed of sound in air is 343 m/s.

Question

Quizplus · Accepted Answer

The frequency heard by the pedestrian can be calculated using the Doppler effect formula:

f' = f ((v_sound ± v_observer)/(v_sound ± v_source))

where f is the frequency emitted by the source (car horn), f' is the frequency heard by the observer (pedestrian), v_sound is the speed of sound in air, v_observer is the speed of the observer (0 m/s for pedestrian), and v_source is the speed of the source (30.0 m/s for the car).

Plugging in the given values: 
f' = 400 ((343 + 0)/(343 + 30.0)) = 438 Hz

Therefore, the pedestrian hears a frequency of 438 Hz which corresponds to option D.

A Car Horn Emits a Frequency of 400 Hz