Calculate open pipe length given resonance.

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To calculate the length of an open pipe needed for resonance at 384 Hz, the speed of sound is given as 343 m/s. The relevant formula is f = nv/2l, where f is frequency, n is the harmonic number (1 for the fundamental frequency), v is the speed of sound, and l is the length of the pipe. The calculation shows that the length of the pipe should be approximately 9.45 meters. Understanding the formula's components, particularly the factor of 2 in the denominator, is crucial for solving similar problems in exams. This approach effectively demonstrates how to derive the required length for resonance in an open pipe.
seker
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Homework Statement



What length of open pipe is needed to give resonance to a 384 Hz sound? Assume the speed of sound to 343 m/s.

Homework Equations



f=\frac{nv}{2l}

The Attempt at a Solution



I am lost as to how to even start this problem.
 
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welcome to pf!

hi seker! welcome to pf! :smile:

what is the (shortest) length (of an open pipe) needed to give a particular wavelength? :wink:
 
This is what I have come up with so far.

(384)(l)=\frac{(1)(343)}{2}

l=9.45m
 
looks ok! :smile:

(btw, do you understand why there's a "2" on the bottom, and would you be able to work it out for yourself in an exam if you couldn't remember the exact formula? :wink:)
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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