Calculating Wave Speed and Wavelength for a Vibrating String

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Homework Help Overview

The discussion revolves around calculating wave speed and wavelength for a vibrating string, given its mass per unit length and tension. The original poster expresses uncertainty about how to begin solving the problem after a long absence from physics studies.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the formula for wave speed and raise questions about unit conversions and the correct application of physical principles. There is an exploration of the relationship between tension, mass per unit length, and wave speed.

Discussion Status

Some participants have offered guidance on the correct formula to use and highlighted the importance of unit consistency. There is acknowledgment of errors in calculations and unit conversions, with ongoing clarification about the correct approach to the problem.

Contextual Notes

Participants note the original poster's long gap since studying physics, which may affect their understanding of the concepts and calculations involved.

ddsMom
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Homework Statement



A long string with a mass/length of 500g/m is placed under a tension of 400N. The string is then vibrated up and down with a period of .425sec.

What is the wave speed?

What is the wavelength of the resulting wave?

I have no idea where to beginI would really like to learn this. It's been 20+ years since I have taken a Physics course.
Thank you!


Homework Equations





The Attempt at a Solution



I have no idea where to begin other than this formula:

v=λ/T

I would really like to learn this. It's been 20+ years since I have taken a Physics course.
Thank you!
 
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what resource are you using? (textbook, on-line notes, ??)
...(here are some very brief notes : http://www.science.marshall.edu/foltzc/211t9.htm )

generally to get a speed, you square root a (Force term divided by an inertia density).
tweak the density so that the units come out right for speed.

sqrt[T/(m/L)].
 
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I did use v=sqrt[T/(m/L)]

so I got v=sqrt[400N/(500g/m)] = .029

Am I on the right track?
 
Changed my g to kg. Thank you so so much for confirming.
 
ddsMom said:
I did use v=sqrt[T/(m/L)]

so I got v=sqrt[400N/(500g/m)] = .029

Am I on the right track?

No. You have made error in calculating square root.
 
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right track, but off by a UNITS error ... recall that Newton is composed of kilo-gram, not gram. (N=kg m/s²)
Always include the units that any numerical value multiplies; kg should cancel inside the sqrt.
 
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