1. You are required to experiment with waves, so you have strung uniform steel w

Question

1. You are required to experiment with waves, so you have strung uniform steel wire between two posts, 100 m apart, and find that the fundamental mode has a frequency of 150 Hz.
a. What is the 3rd harmonic frequency of this wire?
b, What is its fourth overtone?
2. An organ pipe is effectively open at one end, closed at the other, and has a fundamental frequency of 165Hz.
a. How long is the pipe?
b. What should be the fourth resonance frequency for this pipe?
3. Sue's neighbor, Jack, likes loud music in his car. One morning as he sets out driving north at 15 m/s with his car windows open, the recording being broadcast includes a sustained note with a frequency of 550 Hz.
a. Sue is coming home going south toward him at 30 m/s; what frequency do her accurate ears sense?
b. A sound meter 4 m from Jack's radio registers 75 dB coming from it. What would an identical meter 200 m away read from the radio? (Assume uniform distribution; i.e., ignore echo or dead spot effects.)

Explanation / Answer

2)

(a).

¼ = L

¼ (v/f) = L

¼ (334/165) = L

L = 0.5 meter




(b).

¼ (v/f) (2n - 1) = L

¼ (334/f) (2 * 4 - 1) = 0.5

f = 1155 Hz

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