Waves: fundamental frequency of taut cable

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Homework Help Overview

The problem involves determining the fundamental frequency of vibrations in a taut cable, specifically a wire cable supporting a sailboat mast. The cable's length is given as 12 m, with a linear mass density of 350 g/m, and it is subjected to a sideways force resulting in a deflection. The original poster attempts to apply relevant equations related to wave frequency and tension but questions the correctness of their solution.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the definitions of terms used in the equations, such as frequency, tension, and linear mass density. They question which values are given and how to derive the missing information, particularly the actual tension in the cable.

Discussion Status

Some participants have provided hints regarding the misapplication of given values and the need to calculate the actual tension in the cable, suggesting a productive direction for the original poster's inquiry.

Contextual Notes

There is a noted discrepancy between the force applied to displace the cable and the expected tension in the cable, raising questions about the assumptions made regarding the system's setup.

Any Help
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1. Homework Statement

The wire cable supporting the mast of a sailboat has a length of 12 m and a linear mass density of 350 g/m. When pushed sideways at its midpoint with a force of 160 N, the cable deflects by 9.5 cm. What is the frequency of the fundamental mode of vibrations on this cable?

Homework Equations


λn.fn=v and velocity:v=sqrt(T/μ) , lemda λn=2L/n and L= length of string
fn=n/2L . sqrt(T/μ)
fundamental≡ the first mode ⇒ n=1

The Attempt at a Solution


for n=1
f=1/(2*12) .sqrt (160/0.35) =0.89 Hz
but it is incorrect why??
 
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In the equation you use, what are each of the terms? ( IE. what do the letters f, n, L, T and μ stand for?)
Which of these are given?
What other information are you given?
How will you work out the term, which is not given?

As a hint, you don't use one of the given values and you mis-use one of the given values.
 
Merlin3189 said:
what do the letters f, n, L, T and μ stand for?)
Which of these are given?
Any Help said:
velocity:v=sqrt(T/μ)
T=tension=160N
μ=linear mass=0.35kg/m
Any Help said:
L= length of string
Any Help said:
fundamental≡ the first mode ⇒ n=1
f is the frequence
 
Any Help said:
T=tension=160N
The tension should be the tension in the cable.
The value 160N is the force used to displace the cable sideways by 9.5cm.
The tension in the cable would be much greater. (A mast over 12m high would hardly be supported by a tension of 160N on each side.)

So you need to see how you can use the information given, to calculate the tension in the cable.
 

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