PhysicsLAB Worksheet
Doppler Effect

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Use the hint buttons to assist you in answering these questions. Feel free to view correct answers as often as you need always remembering to try and make your first answers as accurate as possible. You must show all of your work on your papers and get then initialed and dated for your notebooks.

1. What is the frequency heard by a person driving at 15 m/sec toward a blowing factory whistle (f = 800 hz) if the speed of sound is 340.6 m/sec?
 
2. What frequency would he hear after passing the factory if he continues at the same speed? 

Refer to the following information for the next three questions.

A car is racing away from a siren at 25 m/sec. The siren is emitting a frequency of 1200 hz. The air temperature is 30ºC.
What is the speed of sound at this temperature? 

What frequency is heard by the person driving the car? 

How fast would he have to travel to hear a frequency that is only 85% of the siren's true frequency? 

Refer to the following information for the next question.

You are standing in the median between the lanes of a N-S highway, listening to five identical cars. At t = 0 sec, all five are at located 343 meters away from you and are moving as shown below. The sound from all five reach your ear one second later. This physlet shows how a moving source affects the apparent frequency heard by a stationary listener.
  1. 30 m/s, steady speed, away from you going N
  2. 30 m/s, steady speed, towards you going N
  3. 30 m/s, steady speed, towards you going S
  4. 30 m/s, steady speed, away from you going S
  5. pulled off on the side of the road
Rank in order, from highest to lowest, the seven frequencies f1 to f5 that you hear at t = 1 s. 

Refer to the following information for the next three questions.

In each diagram, information about the frequencies heard by the listener are based on time.

ABC
DE
In which diagram(s) is the car initially (0 < t < 2) moving away from your position?
 
In which diagram(s) is the car initially (0 < t < 2) moving towards you at a faster rate than it when leaves?
 
In which diagram(s) does the car travel at a constant speed throughout the entire time?
 



 
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