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

In summary, the problem is to find the equations of motion for a pendulum system consisting of a uniform rod of mass m and length l attached to a light rod of length l that is fixed to the ceiling. The system moves in a vertical plane and the coordinates of the center of mass are given by X and Y, while the angles θ and ψ represent the orientations of the rods with respect to the vertical. The Lagrangian method is used to find the equations of motion, with the kinetic energy T and potential energy U given by T = mV^2/2 + IΩ^2/2 and U = mgY, respectively. The velocity V is the velocity of the center of mass relative to a 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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FAQ: Pendulum consists of a rod of mass m attached to a light rod

What is a pendulum?

A pendulum is a weight suspended from a fixed point that can freely swing back and forth under the influence of gravity. It is commonly used in timekeeping devices such as clocks and metronomes.

What is the purpose of the rod in a pendulum?

The rod in a pendulum serves as a support structure for the weight and helps to maintain its stability and balance as it swings.

How does the mass of the rod affect the motion of the pendulum?

The mass of the rod does not significantly affect the motion of the pendulum. The main factor that influences the motion of a pendulum is the length of the string or rod from which the weight is suspended.

How does the length of the light rod impact the period of the pendulum's swing?

The length of the light rod does not have a significant impact on the period of the pendulum's swing. The period, or the time it takes for one complete swing, is primarily determined by the length of the string or rod from which the weight is suspended.

Is there a difference between a pendulum with a light rod and a heavy rod?

The weight of the rod does not have a significant impact on the motion of the pendulum. However, a heavier rod may cause more resistance and decrease the pendulum's amplitude, or the distance it swings from side to side.

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