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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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