How Long Is the Piano String for the 3rd Harmonic?

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Discussion Overview

The discussion revolves around determining the length of a piano string that produces the 3rd harmonic, given that the wavelength is 45.0 cm. Participants explore the relationship between harmonics, wavelengths, and string length, seeking clarification and guidance on the calculations involved.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about how to approach the problem and requests assistance.
  • Another participant suggests creating drawings to visualize the string vibrating at different harmonics, indicating that the third harmonic has three antinodes.
  • A participant notes that the question implies the wavelength is 45 cm and hints that the string length will be between 60 cm and 70 cm.
  • One participant states that no formula is required and proposes a method of scaling from the drawing, explaining the relationship between wavelengths and half wavelengths.
  • Another participant calculates the string length as 67.5 cm based on the relationship of three half wavelengths to the given wavelength.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the method to calculate the string length, with some suggesting visual aids and others providing calculations. The discussion remains unresolved regarding the preferred approach to solving the problem.

Contextual Notes

Participants have not explicitly defined the assumptions regarding the relationship between harmonics and string length, nor have they detailed the mathematical steps involved in their reasoning.

xuhhad
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The 3rd harmonic on a piano string occurs when a 45.0 cm wave is produced. How long is the string.

This question is really confusing can i get some leads to help me out please and thank u
 
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Make three drawings showing a string vibrating at the first, second and third harmonic.
Hint: Third harmonic has three antinodes.

http://en.wikipedia.org/wiki/Vibrating_string

Mark the wave length on the drawing of the third harmonic.
http://en.wikipedia.org/wiki/Wavelength

The question is presumably telling you that one wavelength is 45cm.

Apply basic maths to calculate the length of the string.

I'll let you work it out but I make the answer a number between 60cm and 70cm.
 
Last edited:
OK i understand but i still don't no what formula to use.
 
No formula is required. Scale from the drawing.

One wave length = two half wave lengths = 45cm

So three half wave lengths = 3/2 * 45cm = 67.5cm
 

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