Sum of Normal Modes on a Vibrating String

In summary, the equation on the right, which gives the sum of the first two normal modes, is not a general formula but depends on specific initial conditions. The phase angle in the first normal mode is not included in the equation and the amplitude of the second normal mode is 1/2. These results are not generally true and vary depending on the initial conditions.
  • #1
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Homework Statement



In textbooks, I often see the sum of the first two normal modes given in the equation attached (on the right). I'm wondering how they arrive at that equation based on the general formula (on the left).

I tried subbing in n= 1 and 2 in the general formula, but I'm not sure where to go from there. Where does the phase angle in the first normal mode go? Why is the amplitude of the second normal mode 1/2?
 

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  • #2
The equation on the right is not general, but depends specifically on the initial conditions. Eg., the string's displacement and velocity at t=0.

The fact that the phase angles of the 2 modes are zero and π/2, or that the amplitudes are 1 and 1/2, is not a generally true result.
 

Related to Sum of Normal Modes on a Vibrating String

1. What is the concept of sum of normal modes on a vibrating string?

The sum of normal modes on a vibrating string refers to the total energy or vibration that can be produced by combining multiple individual normal modes on a string. Each normal mode corresponds to a specific frequency at which the string can vibrate, and when these modes are summed together, they create a more complex and varied overall vibration pattern.

2. How is the sum of normal modes on a vibrating string calculated?

The sum of normal modes on a vibrating string is calculated by adding together the amplitudes and phases of each individual normal mode. This can be done using mathematical equations, such as Fourier series, or through experimental measurements of the string's vibration.

3. What is the significance of the sum of normal modes on a vibrating string?

The sum of normal modes on a vibrating string is significant because it helps us understand and analyze complex vibrations and sound waves. By studying the individual normal modes and their contributions to the overall vibration, we can better understand the properties and behavior of the string and the resulting sound produced.

4. How does the sum of normal modes on a vibrating string relate to music?

The sum of normal modes on a vibrating string is closely related to music as it is the basis for understanding the production of sound from stringed instruments. By manipulating the normal modes on a string, musicians can create different notes and melodies, and by analyzing the sum of these modes, we can better understand the science behind music.

5. Can the sum of normal modes on a vibrating string be applied to other systems besides stringed instruments?

Yes, the concept of sum of normal modes on a vibrating string can be applied to other systems and phenomena, such as the vibrations of a drumhead or the oscillations of an electronic circuit. It is a fundamental concept in the study of vibrations and waves, and can be applied to various fields of science and engineering.

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