Fundamental standing wave in Closed tube

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Homework Help Overview

The discussion revolves around calculating the frequency of the fundamental standing wave in a closed tube, specifically an empty test tube with a given length of the air column and the speed of sound in air. The problem is set within the context of wave mechanics and acoustics.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants calculate the frequency using the formula for a closed tube and express concern about the correctness of their answer. There is discussion about the significance of units, particularly whether the answer should be in Hz or KHz, and whether significant figures might affect the outcome.

Discussion Status

Participants are actively engaging with the problem, sharing their calculations and questioning the requirements of the online program regarding units. Some guidance has been offered regarding unit conversion, and there is an acknowledgment of the importance of attention to detail in calculations.

Contextual Notes

There is an implication that the online program may have specific expectations regarding significant figures and units, which has led to confusion among participants. The original poster and others are reflecting on the necessity of careful unit management in their calculations.

stylez03
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Homework Statement


You blow across the open mouth of an empty test tube and produce the fundamental standing wave of the air column inside the test tube. The speed of sound in air is 344 m/s and the test tube acts as a stopped pipe.

If the length of the air column in the test tube is 14.0 cm, what is the frequency of this standing wave?

L = 0.14m
V = 344 m/s
Closed Tube


Homework Equations



Closed Tube Frequency = Fn = nVair / 4L


The Attempt at a Solution



F1 = 1*344 / 4*0.14 = 614khz

I thought this was the right answer, but the online program says it's incorrect.
 
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i got the same answer.

That's the standing wave...perhaps it's asking for a resonance frequency? Seeing that it's an online program...maybe it wants more SIG FIGS?
 
stylez03 said:


The Attempt at a Solution



F1 = 1*344 / 4*0.14 = 614khz

I thought this was the right answer, but the online program says it's incorrect.


Is it really KHz?
 
Well the online program already had the units ready, which was khz. Should there be a conversion?
 
The calculation you have done gives an answer in Hz and if the online thing wants it in KHz the yes you will have to convert from Hz to KHz
 
Thanks Kurdt, that seemed to work. I hate the units in some of these problems, guess I should pay attention as well.
 
Yes units are very important. They've probably done that to make you think about them. :smile:
 

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