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FLms
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Homework Statement
A heavy particle is placed at the top of a vertical hoop. Calculate the reaction of the hoop on the particle by means of the Lagrange's undetermined multipliers and Lagrange's Equations. Find the height at which the particle falls of.
Homework Equations
[tex]\frac{d}{dt} \frac{\partial L} {\partial\dot{q}} - \frac{\partial L}{\partial q} = 0[/tex]
The Attempt at a Solution
[tex]L = \frac{1}{2} m (\dot{r}^2 + r^2 \dot{\theta}^2) - mgr cos(\theta)[/tex]
Euler-Lagrange Equation with respect to [itex]r[/itex] becomes:
[tex]m \ddot{r} - m r \dot{\theta}^2 + m g cos(\theta) = \lambda[/tex]
And, with respect to [itex]\theta[/itex]:
[tex]mr^2 \ddot{\theta} + 2 m r \dot{r} \dot{\theta} - mgr sin(\theta) = 0[/tex]
As the radius is constant, it's derivative is zero. So, we have:
[tex]- m r \dot{\theta}^2 + m g cos(\theta) = \lambda[/tex]
[tex]m r^2 \ddot{\theta} - m g sin(\theta) = 0[/tex]
Now, I don't really know what's the next step.
What should I do?
Any help appreciated.