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 19 Hz; if you are moving towards the 'clicker' at 18 m/sec what apparent frequency do you hear instead?
-1.06 Hz
17.99 Hz
20.01 Hz
39.06 Hz
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Question 2
You are riding a bike away from a street musician at 9 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?
447 Hz
433 Hz
428 Hz
452 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 381 Hz, what is the actual frequency of the car horns.
340 Hz
433 Hz
427 Hz
335 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 18 crests every 10 seconds. Shortly afterwards you come to rest on the water and measure the waves to have an actual frequency of 14 every 10 seconds with a wave speed of 13.7 m/sec. How fast was your boat traveling before?
47.9 m/sec
31.3 m/sec
6.0 m/sec
3.9 m/sec
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Question 5
You are speeding away from a loud speaker. If the original frequency of 381 Hz is shifted to 340 Hz, what is your speed away from the speaker?
30 m/sec
36.6 m/sec
41 m/sec
8 m/sec
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Question 6
You are measuring the speed of a projectile using sonar. If a frequency of 190.5 Hz is reflected back at 181.5 Hz, what is the speed of the projectile?
16.9 m/sec
37.8 m/sec
16.1 m/sec
32.4 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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