How to find wavelength with only distance

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SUMMARY

The discussion focuses on calculating the wavelength of sound in air using a metal rod and a tube with closed ends. Given parameters include a length (L) of 1.0 m, a distance (d) of 0.05 m, and sound speeds of 340 m/s in air and 1,000 m/s in metal. The wavelength of air is determined to be 0.68 m, derived from the relationship between frequency and wavelength. Clarifications are made regarding the definition of wavelength, emphasizing that it is the distance between two crests or nodes, not three.

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Homework Statement


zekp8kV.png

A metal rod attached to a tube with both closed ends is stimulated to create waves inside the tube.

If:
L = 1.0 m
d = 0.05 m
Speed of sound in air = 340 m/s
Speed of sound in metal = 1,000 m/s

Calculate the value of x using the wavelength of air.

Homework Equations


Frequency = Velocity / Wavelength

The Attempt at a Solution


The frequency of the the metal is the same as the frequency in air, so:

1,000 / (2*1.0) = 340 / wavelength of air

Because the wavelength of the metal is 2 * L.

340 / 500 = wavelength of air
0.68 = wavelength of air

How do I calculate wavelength with only the distance between two nodes (d)? I need x from wavelength according to the problem's instructions so I have to work backwards but I don't know any formulas for this one.
 
Last edited:
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PhizKid said:
How do I calculate wavelength with only the distance between two nodes (d)?

Wavelength is the distance between two nearest nodes = d. Can you clarify what you are trying to find?
 
voko said:
Wavelength is the distance between two nearest nodes = d. Can you clarify what you are trying to find?

I thought the wavelength was the distance between 3 nodes, since between two nodes is only half the cycle. This is where I'm confused...is the wavelength between two nodes, or is the wavelength between 3 successive nodes? Because I thought the distance between two nodes only completed half the cycle.
 
Sorry, you are right. What I meant to say was distance between two crests, which is what the diagram shows, I think.
 
Wavelength.jpg
 
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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