Fourier sine series for a triangular wave on a finite string

In summary, the conversation discusses finding the Fourier coefficient Bn for a string of length L = 8 that is fixed at both ends and given a small triangular displacement at t=0. The equations used for U0(x) are discussed and it is suggested to find the equation of the two straight line segments forming the triangular displacement. It is also mentioned to ignore a previous answer which was discontinuous and partially parabolic. A humorous quote is made about choosing between cheap, fast, and reliable, suggesting that one can only have two of those qualities.
  • #1
nazmus sakib
5
0

Homework Statement


A string of length L =8 is fixed at both ends. It is given a small triangular displacement and released from rest at t=0. Find out Fourier coefficient Bn.

Homework Equations



what should i use for U0(x) ?

The Attempt at a Solution


fourier sin.png
 
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  • #2
Hello nazmus, :welcome:

ax from 0 to L/2 and x(1-x) from L/2 to L . Oops :nb), I'm not supposed/allowed to give direct answers !
 
  • #3
nazmus sakib said:

Homework Statement


A string of length L =8 is fixed at both ends. It is given a small triangular displacement and released from rest at t=0. Find out Fourier coefficient Bn.

Homework Equations



what should i use for U0(x) ?
First, you need to know what the "small" displacement is. Let's say you lift the center by an amount ##h##, so the center of the string is at ##(\frac L 2,h)##. Now just find the equation of the two straight line segments forming the triangular displacement. Also, I would ignore BvU's answer which is a) discontinuous and b) partially parabolic.
 
  • #4
LCKurtz said:
Also, I would ignore BvU's answer which is a) discontinuous and b) partially parabolic.
No, it was just a typo. I (of course) meant

ax from 0 to L/2 and a(L-x) from L/2 to L
And for the Fourier coefficient calculation it really doesn't matter how big a (or h) is.

All lin good spirit :smile:

Cheap, fast, and reliable. Pick any two
.
 
Last edited:

1. What is a Fourier sine series?

A Fourier sine series is a mathematical representation of a periodic function as an infinite sum of sine functions with different frequencies and amplitudes. It is used to analyze and approximate various types of periodic phenomena, including sound and electromagnetic waves.

2. What is a triangular wave?

A triangular wave is a periodic waveform that has a triangular shape, with equal slopes in both positive and negative directions. It is commonly used to represent oscillating signals in electronics and is also found in natural phenomena, such as ocean waves.

3. How is a Fourier sine series used to represent a triangular wave?

A Fourier sine series can be used to represent a triangular wave by decomposing it into a sum of sine functions with different frequencies and amplitudes that together create the triangular shape. This allows for a more precise analysis and manipulation of the triangular wave.

4. What is a finite string in relation to Fourier sine series?

A finite string refers to a physical object, such as a guitar string, that can be modeled as a one-dimensional string with a finite length. In the context of Fourier sine series, a finite string is used as the medium on which the triangular wave is being represented and analyzed.

5. What are the applications of Fourier sine series for a triangular wave on a finite string?

The applications of Fourier sine series for a triangular wave on a finite string are numerous. Some examples include analyzing the sound produced by vibrating guitar strings, predicting the behavior of ocean waves, and designing electronic circuits that use triangular wave signals.

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