Pendulum consists of a rod of mass m attached to a light rod

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SUMMARY

The discussion focuses on deriving the equations of motion for a pendulum consisting of a uniform rod of mass m and length l, suspended from a light rod fixed to the ceiling. The Lagrangian method is employed, where the Lagrangian is defined as L = T - U, with potential energy U = mgY and kinetic energy T expressed in terms of the center of mass velocity and moment of inertia. The user attempts to calculate the coordinates of the center of mass and the velocities, but expresses confusion regarding the correct moment of inertia and angular velocity definitions for the system.

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Homework Statement


A pendulum consists of a uniform rod of mass m and length l hanging from the bottom end of a light rod of length l which top end is fixed to the ceiling. (see file attached)
System moves in a vertical plane. Find equations of motion.

Coordinates of the center of mass (X,Y)
angles θ and ψ of the light rod and the rod of mass m with the vertical respectively.

Homework Equations



Lagrangian method

L=T-U
U=mgY
T=mV2/2 + IΩ2/2

V is the velocity of the center of mass respect to a system at rest which origin is the top end of the light rod.

The Attempt at a Solution



X=l/2sinψ + lsinθ
Y=-l/2cosψ -lcosθ

|V|2= l2/4[itex]\dot{ψ}[/itex] + l2[itex]\dot{θ}[/itex]2 + l2[itex]\dot{ψ}[/itex][itex]\dot{θ}[/itex]cos(ψ-θ)

I relative to the top end of the rod of mass m I=ml2/3
ω=[itex]\dot{ψ}[/itex]

then i will plug this into L= T-U and the fin the Euler- Lagrange equations.
but i am not sure about I and ω.

I am confused. My first attempt was to choose same X,Y,V but I relative to the center of the rod of mass m I= ml2/2 and ω=[itex]\dot{ψ}[/itex]+[itex]\dot{θ}[/itex]
 

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