Wave speed, freq, and period of wave on a string

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SUMMARY

The discussion focuses on calculating the wave speed, frequency, and period of a vibrating guitar string with specific parameters. The string has a length of 1.5 m, a tension of 76 N, and a linear mass density of 4.9 g/m. The correct wave speed is calculated using the formula v = √(T/μ), resulting in a speed of 124.54 m/s. The frequency is derived from the relationship v = fλ, yielding a frequency of 183.147 Hz and a period of 0.00546 s, although the calculations were initially questioned for accuracy.

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  • Understanding of wave mechanics and properties of waves
  • Familiarity with the tension formula in strings
  • Knowledge of linear mass density calculations
  • Ability to manipulate and apply wave equations
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  • Study the relationship between tension and wave speed in strings
  • Learn about the effects of boundary conditions on wave behavior
  • Explore the concept of harmonic frequencies in string instruments
  • Investigate the impact of string length and mass on frequency and period
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This discussion is beneficial for physics students, music instrument makers, and anyone interested in the mechanics of vibrating strings and wave phenomena.

dinospamoni
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Homework Statement



A musician frets a guitar string of length 1.5 m at x = 0.34 m with one finger, and simultaneously plucks the string at x = 0.17 m with another finger (raising it to a height h = 2.1 mm. Both fingers are simultaneously removed from the string, and it is allowed to vibrate. The string has a tension of 76 N, and a linear mass m = 4.9 g/m.

Homework Equations



v=\sqrt{\frac{T}{\mu}}
where
\mu=\frac{mass\,in\,kg}{Length\,in\,m}

v=f\lambda



The Attempt at a Solution



I started off converting the linear mass:

4.9\frac{g}{m} \times\frac{1 kg}{1000 g} = .0049\frac{kg}{m}

Then I plugged that into the equation:

v=\sqrt{\frac{76 N}{.0049\frac{kg}{m}}}

and got v=124.54 m/s

From here I used v=f\lambda
where \lambda=.68 m

and got frequency = 183.147 Hz

Taking the reciprocal of that:

Period = .00546 s

These aren't the right answers, but I don't see where I went wrong

Also, picture attached
 

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You don't say exactly what is being asked. You have calculated, correctly I believe, the period as though the fret finger is still in place, but is it what was asked for?
 
I included what was asked for in the title, but forgot to include it in the question. It's asking for the wave velocity, frequency, and period.

I accounted for the finger being lifted off by making the wavelength twice the interval between the finger and the origin. Is that not right?
 
dinospamoni said:
I included what was asked for in the title, but forgot to include it in the question. It's asking for the wave velocity, frequency, and period.

I accounted for the finger being lifted off by making the wavelength twice the interval between the finger and the origin. Is that not right?
No, that's what it would be if the finger were left in place. But even then, 1.5m is not twice 0.34m. How do you propose to bring 1.5m into the equation?
 

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