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Energy in a pendulum (SHM)

Okay, I have a small problem. Treating a pendulum as a simple harmonic oscillation, And using           v(max)=A (omega) you get

                   v(max)=A (sqrt(g/L))

 

 

But using conservation of energy, and the approximation that sin(theta)=theta for small angles and radians, you get

                 v(max)=A(sqrt(2g/L))

 

(see the attached file)

 

I have looked in 6 different texts and a bunch of forums and can't find an explaination.

Can anyone help?

 

Dave McPhee 

 

 

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Permalink Reply by Stephen Fuerderer on December 15, 2010 at 8:54pm
Hi Dave. I don't have an answer for you, but you may have more luck appealing to the wider audience of instructors on the AP Physics discussion board at AP Central. If I figure this out I"ll be sure to let you klnow.
Merry Christmas
Permalink Reply by Dave McPhee on December 16, 2010 at 1:05am

I think I figured it out! The angle in the small triangle with A and h is not theta, it is 1/2 theta. That makes all well I think!

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