Changing string length -> changing fundamental freq.

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A 0.5 m violin string has a fundamental frequency of 440 Hz, and the discussion revolves around calculating the new length required for a fundamental frequency of 528 Hz. The calculated length for the new frequency is 0.416 m, which aligns with the principle that a shorter string produces a higher frequency. The participant questions how the wave velocity remains at 440 m/s despite shortening the string, suggesting that tension or linear density might change. It is clarified that if the tension remains the same as in the longer string, the wave velocity will also remain unchanged. The discussion emphasizes the relationship between string length, frequency, and wave velocity in a fixed tension scenario.
Lavabug
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Homework Statement


Don't have the solution, just want to check if I did this properly.

A 0.5 m violin string fixed at both ends has its first harmonic or fundamental frequency at 440 Hz. Assuming the string is non dispersive, calculate the length it should have so its new fundamental frequency will be 528 Hz.


Homework Equations


The nth harmonic's wavelength is 2L/n, where L is the length of the string.
\lambda\upsilon = v

The Attempt at a Solution


Apparently the phase velocity of the given fundamental harmonic is 440m/s.

If I want a new \upsilon of 528 Hz, I'd need a string of length = v/2\upsilon, so 440/2(528) = 0.416m. A shorter string = higher frequency which makes sense, but my question is: how is the velocity of the wave still 440 m/s? I just shortened the string, wouldn't the tension be greater necessarily(or the linear density decreased as a consequence), hence the velocity would change?

For the sake of simplicity: does the new fundamental harmonic at 528Hz still propagate at 440m/s along the string?
 
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Lavabug said:
A shorter string = higher frequency which makes sense, but my question is: how is the velocity of the wave still 440 m/s? I just shortened the string, wouldn't the tension be greater necessarily(or the linear density decreased as a consequence), hence the velocity would change?

You can choose the tension in the shorter string the same as in the longer one. (It is not stretched to the original length). So the linear density stays the same.




ehild
 
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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