How Do You Apply the Lagrange Equation to a Hoop at Theta Equals Zero?

[Shahbakht]

Homework Statement

Two equal masses are glued to a massless hoop of radius R that is free to rotate about its center in a vertical plane. The angle between the masses is 2*theta. Find the frequency of small oscillations.

I dont get that if two masses, so where do we take the postion vector from? From the centre?

Relevant Equations

d/dt(dL/dtetha)=dL/dtetga

I couldn't even get the position vector. Help!

 

[BvU]

Hello Shahbakht, !

Can you do it for $\theta = 0$ ? We need some effort from you before we are allowed to assist -- see guidelines