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 27 m/sec what apparent frequency do you hear instead?
13.70 Hz
9.21 Hz
6.30 Hz
10.79 Hz
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Question 2
You are riding a bike away from a street musician at 13.5 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?
423 Hz
430 Hz
450 Hz
457 Hz
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Question 3
You are in an ambulance driving towards an accident at 34 m/sec. You hear the horns of the cars in the accident sounding at a frequency of 320 Hz, what is the actual frequency of the car horns.
352 Hz
356 Hz
291 Hz
288 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 27 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 11.3 m/sec. How fast was your boat traveling before?
72.3 m/sec
2.6 m/sec
1.8 m/sec
49.7 m/sec
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Question 5
You are speeding away from a loud speaker. If the original frequency of 320 Hz is shifted to 286 Hz, what is your speed away from the speaker?
40 m/sec
10 m/sec
30 m/sec
36.1 m/sec
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Question 6
You are measuring the speed of a projectile using sonar. If a frequency of 160 Hz is reflected back at 146.5 Hz, what is the speed of the projectile?
25.2 m/sec
28.7 m/sec
31.1 m/sec
31.3 m/sec
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Question 7
In what direction was the projectile in
Question 6
moving relative to the sonar device?
towards the sonar
away from the sonar
cannot be determined
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William A. Hilburn
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