A pipe of length 80 cm is open at both ends. A second pipe, closed at one end, has the same fundamental frequency as the open pipe. The length of the second pipe is:
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Open pipe fundamental: \(v/2L\), closed pipe fundamental: \(v/4L\).
Step 1: Open pipe fundamental. f₁ = v/(2L₁); with L₁ = 80 cm, f₁ = v/160. Step 2: Closed pipe fundamental. f₂ = v/(4L₂). Step 3: Equating frequencies. v/160 = v/(4L₂). Step 4: Solving for L₂. 4L₂ = 160 → L₂ = 40 cm. Step 5: Physical note. A closed pipe's fundamental is half that of an open pipe of the same acoustic length scale. Step 6: Conclusion. The required closed pipe length is 40 cm.