Problem with Lagrange first kind equations

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SUMMARY

The discussion focuses on solving Lagrange's first kind equations for two masses constrained by a solid rod of length B, moving in concentric circles with radii R1 and R2. The constraint equation is defined as B = R1^2 + R2^2 - 2R1R2cos(θ1 + θ2). The user presents their Lagrangian as L = (m/2)(R1^2ω1^2 + R2^2ω2^2) - mg(sinθ1 + sinθ2) and derives two equations of motion involving angular accelerations and Lagrange multipliers. The user seeks clarification on the correctness of their approach and the form of the Lagrangian.

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Homework Statement


Two masses move in a plane restricted to concentric circles with radii R1 and R2. They are joined by a solid rod of length B. Use Lagrange first order equations to find the equilibrium point


Homework Equations


Constraint due to the solid bar: B = R12 + R22 -2R1R2cos(θ1 + θ2), where θ1 and θ2 are the polar coordinates of the masses.

The Attempt at a Solution


My Langrangian is as follows: L = (m/2)(R12ω12+R22ω22)-mg(sinθ1+sinθ2)
By substituing in this expression http://en.wikipedia.org/wiki/Lagrangian_mechanics#Lagrange_equations_of_the_first_kind I find two equations of motion:
-mgcos(θ1)+mR12+α1 + R1R2sin(θ1 - θ2)λ1 = 0
-mgcos(θ2)+mR22+α2 - R1R2sin(θ1 - θ2)λ2 = 0
where α1 and α2 are the angular accelerations of the masses, and the λs are the Lagrange multipliers. I can't solve this equations, though. Is there any method of solving them that I cannot find or is it that my whole procedure is wrong?
 
Last edited:
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Can you show us what your Lagrangian looks like, that you use to derive these equations of motion?
You denoted the constraint by ##L##, but I don't think that expression is your Lagrangian because I don't see a kinetic term.
 
Sorry, its a bit confusing because the length of the bar is L. I'll change it to B and edit the rest.
 

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