You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive the frequency as 1470 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the frequency as 1400 Hz. What is the frequency of the siren in the police car? The speed of sound in air is 343 m/s.
A)1300 Hz
B)1320 Hz
C)1430 Hz
D)1360 Hz
E)1370 Hz

Question

Quizplus · Accepted Answer

Using the Doppler effect formula for sound, the frequency of the siren can be calculated. When the police car approaches, the frequency is higher, and when it moves away, the frequency is lower. Solving the equations for both scenarios gives the actual frequency of the siren as approximately 1430 Hz.

You Are Driving Along a Highway at 35