Waves: fundamental frequency of taut cable

Click For Summary
The discussion centers on calculating the fundamental frequency of a taut cable supporting a sailboat mast, given its length of 12 m and linear mass density of 350 g/m. The initial calculation incorrectly uses a tension of 160 N, which is the force applied to displace the cable, not the actual tension in the cable. To find the correct frequency, the actual tension must be determined, as it is likely much greater than 160 N due to the cable's support role. Key variables in the equations include frequency (f), mode number (n), length (L), tension (T), and linear mass density (μ). Properly identifying and calculating these parameters is essential for an accurate solution.
Any Help
Messages
79
Reaction score
2
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??
 
Physics news on Phys.org
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.
 
Thread 'Correct statement about size of wire to produce larger extension'
The answer is (B) but I don't really understand why. Based on formula of Young Modulus: $$x=\frac{FL}{AE}$$ The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A## I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...

Similar threads

  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
3
Views
4K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 2 ·
Replies
2
Views
4K
Replies
7
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
6
Views
1K