Equations of motion for a compound pendulum

In summary, the conversation discusses deriving equations of motion for a compound pendulum, with given parameters and coordinates. The coordinate system is described and the expressions for the center-of-mass in terms of Euler angles are found. The next step is to derive the expression for the components of angular velocity in terms of Euler angles, but further assistance is needed.
  • #1
msntito
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Homework Statement


To derive the equations of motion for a compound pendulum. Pendulum parameters are: mass M, mass moment of inertia= Ixx,Iyy,Izz,Ixy,Iyz,Izx, Euler angles theta, phi & psi and their time-derivatives theta_dot, phi_dot, & psi_dot, and coordinates of center-of-mass (x,y,z)

The coordinate system is give as; X & Y axis in horizontal plane, while Z axis point downwards. (SEE FIGURE attached with this post)
https://www.physicsforums.com/attachment.php?attachmentid=27054&stc=1&d=1279608886

Homework Equations


Kinetic energy, T = 0.5 [tex]\omega * I * \omega[/tex]
Potential energy, V = -m*g*z
Lagrangian, L = T - V

The Attempt at a Solution


I have found the expression of c-o-m in terms of Euler angles:
x = l*sin(theta)*cos(psi)
y = l*sin(theta)*sin(psi)
z = l*cos(theta)
where, l is the distance between hinge point and c-o-m, and theta is inclination from Z axis, psi is angle between "l*sin(theta)" and X axis.

Now, need to derive the expression for components of angular velocity in terms of Euler angles. How should I do that? Please help.
 
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  • #2
The figure of the physical setup is not available. We cannot help you without it.
 

1. What is a compound pendulum?

A compound pendulum is a physical system consisting of a rigid body or mass suspended from a fixed point, with the motion of the body controlled by gravity and other external forces. It differs from a simple pendulum in that the mass is not concentrated at a single point, but is distributed along its length.

2. What are the equations of motion for a compound pendulum?

The equations of motion for a compound pendulum are derived from Newton's laws of motion and involve the pendulum's mass, length, and moment of inertia. They describe the pendulum's angular displacement, velocity, and acceleration as a function of time and external forces acting on it.

3. How do the equations of motion differ from a simple pendulum?

The equations of motion for a compound pendulum are more complex than those of a simple pendulum due to the distribution of mass along its length. They also take into account the effects of external forces, such as air resistance and friction, which are often negligible in a simple pendulum.

4. Can the equations of motion be used to predict the behavior of a compound pendulum?

Yes, the equations of motion can be used to predict the angular displacement, velocity, and acceleration of a compound pendulum at any point in time. However, these predictions may not be completely accurate due to factors such as imperfections in the physical system and external disturbances.

5. What real-world applications use the equations of motion for compound pendulums?

The equations of motion for compound pendulums are used in various fields, including mechanical engineering, physics, and robotics. They are used to analyze and design pendulum-based systems, such as clock mechanisms, suspension bridges, and robotic arms.

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