Finding the relationship between wave speed and tension in a standing wave

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SUMMARY

The relationship between wave speed and tension in a standing wave on a string is defined by the equation v = √(T/μ), where v is the wave speed, T is the tension, and μ is the linear mass density. In an experiment with a string length of 1.62 m and a frequency of 48.2 Hz, various tensions were applied, resulting in corresponding wavelengths and calculated wave speeds. The experimental values showed wave speeds of 52.06 m/s, 78.08 m/s, 156.17 m/s, and 312.34 m/s for tensions of 0.981 N, 1.962 N, 3.924 N, and 7.848 N respectively. The theoretical relationship confirms that for a fixed tension, the wave speed remains constant, while varying frequency alters the wavelength.

PREREQUISITES
  • Understanding of wave mechanics and standing waves
  • Familiarity with the equations v = fλ and v = √(T/μ)
  • Basic knowledge of experimental physics and data collection
  • Ability to interpret graphs and experimental results
NEXT STEPS
  • Study the derivation of the wave speed equation v = √(T/μ)
  • Explore the impact of varying frequency on wavelength in standing waves
  • Learn about linear mass density (μ) and its calculation for different strings
  • Investigate graphing techniques for plotting experimental data against theoretical predictions
USEFUL FOR

Students studying physics, particularly those focusing on wave mechanics, as well as educators and researchers interested in experimental methods for demonstrating wave properties in strings.

Eutrophicati
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Homework Statement


The problem is the same as the title; to find the relation between wave speed and tension for a standing wave in a string. (Fixed ends)

Given data (from the experiment)

String length = 1.62m, mass is negligible
Frequency = 48.2 Hz
Basically one end of the string was attached to a vibrator with adjustable frequency and the other end suspended across a pulley from where weights could be attached.

These are the recorded results:
Tension :: Number of nodes
0.981 - 4
1.962 - 3
3.924 - 2
7.848 - 1

Homework Equations


v=fλ
v = √(t/μ)

y = (x-1)/2
I used this last one to find the *number of wavelengths* (not the wavelength itself) in the standing wave where x is the number of nodes.

The Attempt at a Solution



I used the number of nodes to calculate the wavelength (length provided as 1.62)
Tension :: wavelength
0.981 - 1.08
1.962 - 1.62
3.924 - 3.24
7.848 - 6.48

And I used
v=fλ, where f = 48.2 to calculate wave speeds. I got 52.06; 78.08; 156.17; 312.34.

I also used v = √(t/μ) to calculate a theoretical speed to plot against the experimental, but I got the same value every time by that method (around 3.967 ms-1).

Well, at the moment, I just want to know what the relationship between tension and wave speed SHOULD be theoretically. (just an equation)
I'm hopelessly confused right now...

Edit: If I can understand the relation I should be able to plot a graph for my experimental values, hopefully I can make some sense out of the results

Edit 2: I thought of this earlier but I keep loosing track since I have no firm grasp on the concept
v = √(t/μ)
Isn't THIS the relation between wave speed and tension itself? :s
 
Last edited:
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Starting from the last question, yes ##v=\sqrt{T/\mu}## is the correct equation relating the propagation speed to the tension. For a fixed tension, you get a fixed speed. If you vary the frequency, you simultaneously vary the wavelength because the product ##\lambda f## is fixed. Is this an experiment where you fixed the frequency and varied the tension until you got a certain number of nodes? Please describe what you did to get the numbers you posted. Specifically, what did you do to get the pairs of tensions and wavelengths. Also, please remember to attach units to any numbers that have dimensions. This is particularly important in lab experiments.
 

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