Standing Waves on a String (Melde's Experiment)

AI Thread Summary
To determine the mass needed for a standing wave pattern with 6 antinodes, the relationship between tension, mass, and wavelength must be analyzed. The tension in the string is directly related to the mass hanging over the pulley, and the frequency of oscillation is influenced by the wavelength. The equations provided indicate that the change in mass can be calculated by understanding the relative changes in wavelength and tension as the number of antinodes increases. Clarification is sought on deriving the final equation after establishing T=mg, highlighting the need for a diagram to visualize the problem. Understanding these principles is crucial for solving the standing wave problem effectively.
CHurst5841
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The problem is as follows:

"A string exhibits standing waves with 4 antinodes when a mass of 200 g is hanging over the pulley (see attached figure). What mass will produce a standing wave pattern with 6 antinodes?"

The equations that I have found in the relevant section of the text are as follows:

v=\sqrt{\frac{T}{\mu}}

v=f\lambda

f=\frac{1}{\lambda}\sqrt{\frac{T}{\mu}}

T=mg

\frac{1}{n}=\frac{1}{Lf}\sqrt{\frac{T}{\mu}}=[\frac{1}{Lf}\sqrt{\frac{g}{\mu}}}]\sqrt{m}

Where...
T = tension in the spring as supplied by the weight of the hanging mass
mu = linear density of the string
lambda = wavelength
f = frequency of oscillation
m = mass suspended from spring
g = gravitational constant
L = length of the string

I've attached the diagram referenced above for further illustration.

http://img180.imageshack.us/img180/3735/sc002c9a37ww1.th.jpg

I have no idea where to even begin with the problem given the lack of information provided by the question.

Please help!
 
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All the information you need is given. You need to find the relative change in the wavelength to determine the relative change in velocity, and from that determine the relative change in tension, and ultimately the relative change in the mass.
 
therez no diagram attached to it ... can u please attach it again or give us a link for the diagram !
 
Razi Rehman said:
therez no diagram attached to it ... can u please attach it again or give us a link for the diagram !


and can u explain how u got the last eqn after T=mg
 
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