You are driving along a highway at 25 m/s when you hear the siren of an emergency vehicle traveling in the opposite direction on the other side of the highway. When the vehicle is approaching you, you hear the frequency of the siren as 2380 Hz, but when it is past you the frequency becomes 1680 Hz. What is the speed of the vehicle? The speed of sound in air is 343 m/s.
A) 35 m/s
B) 32 m/s
C) 30 m/s
D) 41 m/s
E) 50 m/s

Question

Quizplus · Accepted Answer

Using the Doppler effect formula for sound, the speed of the vehicle can be calculated. The observed frequency when the vehicle approaches is higher, and when it moves away, it is lower. Solving the equations for both scenarios gives the speed of the vehicle as approximately 35 m/s.

You Are Driving Along a Highway at 25 M/s When