Practice Problems
Doppler Effect
Directions:
On this worksheet, you may assume that the speed of sound in air is 340 m/sec unless otherwise stated.
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Question 1
A 'clicker' is sounding at 10 Hz; if you are moving towards the 'clicker' at 25 m/sec what apparent frequency do you hear instead?
10.74 Hz
9.26 Hz
6.00 Hz
14.00 Hz
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Question 2
You are riding a bike away from a street musician at 12.5 m/sec; when the trumpet player hits an 'A'. You know that the frequency of an 'A' should be 440 Hz, what apparent frequency do you hear instead?
430 Hz
450 Hz
456 Hz
424 Hz
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Question 3
You are in an ambulance driving towards an accident at 41 m/sec. You hear the horns of the cars in the accident sounding at a frequency of 271 Hz, what is the actual frequency of the car horns.
304 Hz
242 Hz
308 Hz
238 Hz
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Question 4
You are riding in a boat into oncoming waves and measure the frequency of the waves to be 25 crests every 10 seconds. Shortly afterwards you come to rest on the water and measure the waves to have an actual frequency of 5 every 10 seconds with a wave speed of 13.7 m/sec. How fast was your boat traveling before?
54.8 m/sec
82.2 m/sec
3.4 m/sec
2.3 m/sec
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Question 5
You are speeding away from a loud speaker. If the original frequency of 271 Hz is shifted to 230 Hz, what is your speed away from the speaker?
8 m/sec
29 m/sec
51.4 m/sec
61 m/sec
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Question 6
You are measuring the speed of a projectile using sonar. If a frequency of 135.5 Hz is reflected back at 123 Hz, what is the speed of the projectile?
30.9 m/sec
34.6 m/sec
31.4 m/sec
27.2 m/sec
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Question 7
In what direction was the projectile in
Question 6
moving relative to the sonar device?
cannot be determined
towards the sonar
away from the sonar
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William A. Hilburn
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