# Homework Help: Standing Waves on a String (Melde's Experiment)

1. Jan 16, 2007

### CHurst5841

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 [Broken]

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

Last edited by a moderator: May 2, 2017
2. Jan 17, 2007

### OlderDan

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.

3. Apr 8, 2010

### Razi Rehman

therez no diagram attached to it ..... can u plz attach it again or give us a link for the diagram !!

4. Apr 8, 2010

### Razi Rehman

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