Finding the Lagrangian Matrix for Two-Spring Systems

In summary, the conversation is about solving a problem involving a second system with masses on a linear spring. The person is unsure about how to approach part (a) and is asking for clarification about the n's in the equation. They are confident about solving parts (b) and (c) using standard linear algebra methods. The problem asks for the person to find two matrices, T and V, for the kinetic and potential energy respectively. The person is unsure about how to express these energies in matrix form and asks for clarification.
  • #1
MattIverson
3
0

Homework Statement


The problem is attached. I'm working on the second system with the masses on a linear spring (not the first system).
I think I solved part (a), but I'm not sure if I did what it was asking for. I'm not sure exactly what the question means by the... L=.5Tnn-.5Vnn. Namely, I'm not sure what the n's are and what they represent, so I'm worried that I'm missing something. I also am not sure about the equillibrium position...
Then I'm pretty sure I can do part (b) and (c), but I'm wondering if I just find the eigenvector and values like a normal linear algebra problem. Do I simply just take the matrix I have and operate on it?
Screen Shot 2018-10-27 at 10.41.39 PM.png

Homework Equations


L=T-V
e^-iwt
d/dt(dL/dqdot)-(dL/dq)

The Attempt at a Solution


Attached (for the second system). I'm pretty sure I can figure out (1) if I figure out (2).
Pt1.png
pt2.png
 

Attachments

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  • #2
You didn't do what was asked for in part (a). It's asking you to find two matrices, ##\mathbf T## and ##\mathbf V##, for one thing.

In the Lagrangian, you have for the kinetic energy ##T=\frac 12 m(\dot x_1^2 + \dot x_2^2)##. You can write this as
$$T = \frac 12 \begin{pmatrix}\dot x_1 & \dot x_2 \end{pmatrix} \begin{pmatrix} m & 0 \\ 0 & m \end{pmatrix}\begin{pmatrix}\dot x_1 \\ \dot x_2 \end{pmatrix}.$$ The matrix of masses is the matrix ##\mathbf T## you're being asked to find. You can express the potential energy similarly in terms of a matrix.
 

1. What is the Lagrangian matrix for a two-spring system?

The Lagrangian matrix, also known as the Hessian matrix, is a square matrix used in the study of dynamics and control systems. It is commonly used to represent the kinetic and potential energy of a system and can be used to derive the equations of motion for a two-spring system.

2. How do you find the Lagrangian matrix for a two-spring system?

To find the Lagrangian matrix for a two-spring system, you first need to determine the kinetic and potential energy functions for the system. Then, you can use the Lagrange's equations to derive the equations of motion and obtain the Lagrangian matrix as a function of the system's variables.

3. What information can be obtained from the Lagrangian matrix for a two-spring system?

The Lagrangian matrix provides crucial information about the dynamics of a two-spring system. It can be used to determine the equations of motion, predict the system's behavior over time, and analyze stability and control of the system.

4. What are the advantages of using the Lagrangian matrix for a two-spring system?

The Lagrangian matrix offers several advantages in the study of two-spring systems. It provides a concise representation of the system's dynamics, allows for the use of powerful mathematical tools, and simplifies the analysis of complex systems with multiple degrees of freedom.

5. Are there any limitations to using the Lagrangian matrix for a two-spring system?

While the Lagrangian matrix is a powerful tool, it does have some limitations. It is not suitable for systems with non-conservative forces or complex frictional effects. Additionally, it may be challenging to obtain the kinetic and potential energy functions for certain systems, making it difficult to use the Lagrangian matrix approach.

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