- #1
Caltez
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Homework Statement
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A simple pendulum with l = 9.8m satisfies the equation:
[tex]\ddot{\theta} + \sin{\theta} = 0[/tex]
if [tex]\Theta_{0} = A[/tex]
Show that the period T is given by:
[tex]T = \int_0^\frac{\pi}{2}\left(\frac{1}{(1 - \alpha \sin^2{\phi})^\frac{1}{2} }\right)d\phi[/tex]
where,
[tex]\alpha=\sin^2{\frac{1}{2}\Theta_{0}}[/tex]
2. Relevant equation
It seems that I can use:
[tex]t=\int\left(\frac{1}{\pm(\frac{2E}{m}-\frac{k}{m}x^2)^\frac{1}{2}}\right)dx[/tex]
to find a T expression
The Attempt at a Solution
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I start with:
[tex]t=\int\left(\frac{1}{\pm(\frac{2E}{m}-\frac{k}{m}\theta^2)^\frac{1}{2}}\right)d\theta[/tex]
I find the terms in the rational:
[tex]\frac{2E}{m}=\frac{2}{2m}(m\dot{\theta}^2 + \omega_{0}^2 \theta^2)[/tex]
[tex]k=\omega_{0}^2 m[/tex]
Substitute back into t:
[tex]t=\int\left(\frac{1}{\pm(\dot{\theta}^2-\omega_{0}\theta^2 + \omega_{0}\theta^2)^\frac{1}{2}}\right)d\theta[/tex]
which is just [tex]\ln{\dot{\theta}}[/tex]
at this point I am doubting whether I am on the right track, any insight would help tremendously!
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