Recent content by Klas

##L = \frac{1}{2}m_1R^2\dot{\theta_1}^2 + \frac{1}{2}m_2R^2(\dot{\theta_1} + \dot{\theta_2})^2 + m_1gRcos\theta_1 + m_2gRcos(\theta_1 + \theta_2) -(\sqrt{(Rcos(\theta_1+ \theta_2)-Rcos(\theta_1))^2+(Rsin(\theta_1+\theta_2)+Rsin(\theta_2))^2)}-l_0)^2## Is what I get. Since: ##\dot{x_1}^2 +...

Fixed it. Any tips on how to deal with ## (\sqrt{x^2-y^2} -l_0)^2) = (\sqrt{(Rcos(\theta_1+ \theta_2)-Rcos(\theta_1))^2+(Rsin(\theta_1+\theta_2)+Rsin(\theta_2))^2)}-l_0)^2## when I'm going to partial derivative it later? Thank you for all your help!

I see what you mean. If I rewrite it as ##L = \frac{1}{2}m_1(\dot{x_1}^2 + \dot{y_1}^2) + \frac{1}{2}m_2(\dot{x_2}^2 + \dot{y_2}^2) - (-m_1gy_1 - m_2gy_2 + \frac{1}{2}k(\sqrt{x^2-y^2} -l_0)^2)## should it be correct then? And if, when I rewrite it with ##\theta_1, \theta_2## this part is going...

I guess you mean it should rather be ##mgRcos(\theta)##. I'm have put potential zero at the bottom so at ##mgRcos0## it should be the max potential energy. Did an edit on the original post

Fun to be here. I found a few post looking similar to my problem but not really what I needed help with so I though I'll sign up and ask from some help! Hope that is all right :smile: /K

Homework Statement Two masses are connected by a weightless spring in a friction-less semicircular well (Picture included). Derive the equations of motion with help of lagrange Homework Equations L = T - U = kinetic energy - potential energy The Attempt at a Solution ##L =...