A pendulum consists of a mass m suspended by a massless spring with unextended length b and. spring constant k. Find Lagrange’s equations of motion(adsbygoogle = window.adsbygoogle || []).push({});

Here's how I set up my equation:

x = lsin(theta)

y = -lcos(theta)

(x=0 at equilibrium, y=0 at the point wehre the pendulum is hung from)

Kinetic energy = 1/2 * m * l^2 * (theta dot)^2

Potential energy = -mglcos(theta) + 1/2 kl^2

L = K - U

So after differentiating, I come up with:

theta double dot = w^2 sin (theta)

Does that look right to you?

I appreciate any help.

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# Homework Help: Problem about Lagrange's equation

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