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 12 Hz; if you are moving towards the 'clicker' at 20 m/sec what apparent frequency do you hear instead?
12.71 Hz
4.80 Hz
11.29 Hz
19.20 Hz
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Question 2
You are riding a bike away from a street musician at 10 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?
453 Hz
432 Hz
427 Hz
448 Hz
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Question 3
You are in an ambulance driving towards an accident at 42 m/sec. You hear the horns of the cars in the accident sounding at a frequency of 478 Hz, what is the actual frequency of the car horns.
419 Hz
545 Hz
537 Hz
425 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 20 crests every 10 seconds. Shortly afterwards you come to rest on the water and measure the waves to have an actual frequency of 7 every 10 seconds with a wave speed of 14 m/sec. How fast was your boat traveling before?
3.6 m/sec
54.0 m/sec
7.5 m/sec
26.0 m/sec
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Question 5
You are speeding away from a loud speaker. If the original frequency of 478 Hz is shifted to 436 Hz, what is your speed away from the speaker?
33 m/sec
31 m/sec
8 m/sec
29.9 m/sec
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Question 6
You are measuring the speed of a projectile using sonar. If a frequency of 239 Hz is reflected back at 229 Hz, what is the speed of the projectile?
34.0 m/sec
14.2 m/sec
32.6 m/sec
14.8 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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