Doppler Effect

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 11 Hz; if you are moving towards the 'clicker' at 20 m/sec what apparent frequency do you hear instead?

17.05 Hz4.95 Hz10.35 Hz11.65 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?

427 Hz432 Hz453 Hz448 Hz

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Question 3 You are in an ambulance driving towards an accident at 38 m/sec. You hear the horns of the cars in the accident sounding at a frequency of 356 Hz, what is the actual frequency of the car horns.

396 Hz320 Hz401 Hz316 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 6 every 10 seconds with a wave speed of 12.7 m/sec. How fast was your boat traveling before?

55.0 m/sec5.4 m/sec29.6 m/sec2.9 m/sec

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Question 5 You are speeding away from a loud speaker. If the original frequency of 356 Hz is shifted to 318 Hz, what is your speed away from the speaker?

30 m/sec41 m/sec36.3 m/sec9 m/sec

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Question 6 You are measuring the speed of a projectile using sonar. If a frequency of 178 Hz is reflected back at 168 Hz, what is the speed of the projectile?

19.1 m/sec32.1 m/sec20.2 m/sec34.0 m/sec

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Question 7 In what direction was the projectile in Question 6 moving relative to the sonar device?

away from the sonartowards the sonarcannot be determined