# Wave speed and length

1. Feb 3, 2014

### ddsMom

1. The problem statement, all variables and given/known data

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!

2. Relevant equations

3. 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!

2. Feb 3, 2014

### lightgrav

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)].

3. Feb 3, 2014

### ddsMom

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

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

Am I on the right track???

4. Feb 3, 2014

### ddsMom

Changed my g to kg. Thank you so so much for confirming.

5. Feb 3, 2014

### Tanya Sharma

No. You have made error in calculating square root.

6. Feb 4, 2014

### lightgrav

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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