How to Solve a Three Mass Four Spring System for Transverse Vibration

mezacom
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Homework Statement


Three equal masses are attached to a string at equal distances from one another and from the ends, which are rasten to supports so that there is a tension T in the string. Compute normal modes and natural frequencies of small transverse vibrations about equilibrium. Describe the normal modes.
HINT: Assume the tension constant, neglect gravity and asume the string weightless.

similar systems:
https://ccrma.stanford.edu/CCRMA/Courses/152/vibrating_systems.html

Homework Equations





The Attempt at a Solution


 
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Welcome to PF!

Hi mezacom! Welcome to PF! :wink:

This is a Three-Mass, Four-Spring System, like the Two-Mass, Three-Spring System in your link.

Show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
 
I know how to solve a three mass four spring system for longitudinal vibration. I have solved it and photo it and you can find it in the link.
I also photo how I think I should start my exercise with transversal vibration.
Did I start solving my problem correctly.
I don’t know how to get rid of all thetas.

http://www.mypicx.com/05272010/mass_spring_solved/
 
To solve this, I first used the units to work out that a= m* a/m, i.e. t=z/λ. This would allow you to determine the time duration within an interval section by section and then add this to the previous ones to obtain the age of the respective layer. However, this would require a constant thickness per year for each interval. However, since this is most likely not the case, my next consideration was that the age must be the integral of a 1/λ(z) function, which I cannot model.
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