Linear density and tension problem

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Homework Help Overview

The discussion revolves around a problem involving the tension in a violin string and its relationship to frequency and wavelength. The original poster presents calculations to determine the necessary change in tension to achieve a specific musical note, E, while questioning the accuracy of their results compared to a textbook answer.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the calculations related to wave speed, linear density, and tension in the string. Some question the validity of the given mass of the string and its implications on the problem setup. Others explore the relationship between wavelength and string length in the context of the problem.

Discussion Status

There are differing interpretations regarding the data provided, particularly concerning the mass of the string and the wavelength. Some participants express confidence in the calculations, while others suggest that the original data may be flawed. The discussion is ongoing with no clear consensus reached.

Contextual Notes

Participants note potential discrepancies in the mass of the string and the wavelength provided, suggesting that the assumptions made in the problem may need to be reconsidered. The original poster's calculations are based on the assumption that certain parameters remain constant during the tuning process.

HHH
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The string on the violin with the highest pitch is the note E, which has a frequency of 329.6 Hz and a wavelength of 1.032 m. If the string has a mass of 180.0 g and a length of 32.0 cm and is currently producing a wave of frequency 328.1 Hz, how much do you need to change the tension in the
string to produce the note E? Assume string length, string mass, and wavelength remain unchanged in the tuning process.

The back of the book says 1.35 N and i keep getting around 591 N

1. Solve for tension in string
v = 328.1*1.032
v = 338.5992 m/s

Linear Density (u) = 0.18/0.32
Linear Density (u) = 0.5625 kg/m

338.5992= sqrt(Ft/0.5625)
338.5992^2 = Ft/0.5625
114649.418*0.5625 = Ft
64490.297 = Ft

2. Solve for tension required for note E
v = 329.6 *1.032
v = 340.1472 m/s

Linear Density (u) = 0.18/0.32
Linear Density (u) = 0.5625 kg/m

340.1472= sqrt(Ft/0.5625)
340.1472^2 = Ft/0.5625
115700.117*0.5625 = Ft
65081.316= Ft

3. Find the difference in tension
Ft = 65081.316 - 64490.297
Ft = 591.019
 
Last edited:
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Your math seems fine, your textbook may be wrong. Unless I'm interpreting it incorrectly.
 
HHH said:
The string on the violin with the highest pitch is the note E, which has a frequency of 329.6 Hz and a wavelength of 1.032 m. If the string has a mass of 180.0 g and a length of 32.0 cm and is currently producing a wave of frequency 328.1 Hz, how much do you need to change the tension in the
string to produce the note E? Assume string length, string mass, and wavelength remain unchanged in the tuning process.

Something is very wrong with the data. The 180 g mass is impossible for a violin string! If it is a steel string, it would mean about 5 mm thick! An E string should have of 0.2-0.3 mm diameter!
That 180 g =0.18 kg should be rather 0.18 g.

Also note that the given wavelength of pitch E (1.32 m) refers to air. The wavelength in the chord is different and defined by the length of the chord.
 
ehild said:
Something is very wrong with the data. The 180 g mass is impossible for a violin string! If it is a steel string, it would mean about 5 mm thick! An E string should have of 0.2-0.3 mm diameter!
That 180 g =0.18 kg should be rather 0.18 g.

Also note that the given wavelength of pitch E (1.32 m) refers to air. The wavelength in the chord is different and defined by the length of the chord.
Is my process and math right? or no?
 
HHH said:
Is my process and math right? or no?
The wavelength is twice the chord length. The speed of the wave in the chord is that length multiplied by the frequency.
 

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