While you are standing on a corner,a police car with a 1-kHz siren drives past you at 30 m/s with its siren on.The speed of sound is 340 m/s.After the car has passed,the frequency you hear is about
A)1.10 kHz
B)1.09 kHz
C)1.00 kHz
D)919 Hz
E)912 Hz

Question

Quizplus · Accepted Answer

First, we need to determine whether the frequency we hear will be higher or lower than the actual frequency of the siren. Since the car is moving towards us, the waves of sound from the siren will be compressed, leading to a higher frequency being perceived. This phenomenon is known as the Doppler effect.

Next, we can use the formula for the Doppler effect to calculate the perceived frequency:

f' = f(v ± vd) / (v ± vs)

where f is the actual frequency of the siren, v is the speed of sound, vd is the speed of the detector (in this case, us), and vs is the speed of the source (in this case, the car).

Plugging in the given values, we get:

f' = 1000(340 + 30) / (340 - 30) = 919 Hz

Therefore, the answer is D) 919 Hz.

While You Are Standing on a Corner,a Police Car with a 1-KHz