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 23 m/sec what apparent frequency do you hear instead?
14.35 Hz
9.32 Hz
10.68 Hz
5.65 Hz
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Question 2
You are riding a bike away from a street musician at 11.5 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?
431 Hz
449 Hz
455 Hz
425 Hz
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Question 3
You are in an ambulance driving towards an accident at 39 m/sec. You hear the horns of the cars in the accident sounding at a frequency of 291 Hz, what is the actual frequency of the car horns.
329 Hz
324 Hz
258 Hz
261 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 23 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 m/sec. How fast was your boat traveling before?
72.8 m/sec
3.6 m/sec
2.3 m/sec
46.8 m/sec
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Question 5
You are speeding away from a loud speaker. If the original frequency of 291 Hz is shifted to 252 Hz, what is your speed away from the speaker?
45.6 m/sec
29 m/sec
53 m/sec
9 m/sec
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Question 6
You are measuring the speed of a projectile using sonar. If a frequency of 145.5 Hz is reflected back at 134 Hz, what is the speed of the projectile?
26.9 m/sec
29.6 m/sec
31.3 m/sec
29.2 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
cannot be determined
away from the sonar
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William A. Hilburn
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