How Do Nodes Form on a Vibrating String for the nth Harmonic?

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To prove that there are n-1 nodes on a string fixed at both ends for the nth harmonic, one can start with the relationship between harmonic frequencies and wavelengths. The wavelength is determined by the formula (2/n) times the length of the string. Understanding the sine function's properties is crucial, as it represents the string's shape under given boundary conditions. This mathematical approach will clarify the distribution of nodes along the string. Further exploration of harmonic frequencies will lead to a comprehensive understanding of node formation.
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Prove that there are n-1 nodes on a string fixed at both ends for the nth harmonic.

It is simple to show this using a diagram.

[PLAIN]http://www.space-matters.info/img/nodesandmodes.jpg

However, is there a way to show this mathematically?
 
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You probably have to go through the harmonic frequencies and harmonic wavelengths - once you have wavelength and you know how it depends on the initial length of the string, the rest should be obvious.
 
Think of the properties of the sine function (which is the shape of the string with the given boundary conditions.)
 
Borek said:
You probably have to go through the harmonic frequencies and harmonic wavelengths - once you have wavelength and you know how it depends on the initial length of the string, the rest should be obvious.

Wavelength = (2/n)*length of string

Can I get a hint on what to do next?
 
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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