Lagrangian for a rheonomic constraint?

In summary, the Lagrangian for a system with a rheonomic constraint remains unchanged in the process of deriving the Euler-Lagrange equation. As long as the constraint is holonomic and the force is conservative, the Lagrangian is still equal to the difference between the kinetic and potential energies. The only difference is that there may be a time-dependent term in the Lagrangian, but this does not affect the use of the Euler-Lagrange equation.
  • #1
adartsesirhc
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How does a Lagrangian change for a system with a rheonomic constraint? As far as I can see in the derivations, it shouldn't seem to matter, but I just want to make sure.

And if I have a rheonomic constraint, what should I do with the time? Should I just ignore it and use the Euler-Lagrange equation normally, or should I treat it is a generalized coordinate?

thanks.
 
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  • #2
in fact we can obtain every thing from the process of the derivation of the Euler-Lagrange equation.
as long as the constraint is a holonomic constraint,and the F is conservative(so F=V's derivative),the L is T-V.
and the follow things have no differences with the situations which have no such rheonomic constraint,except that there may be a time-concerned term,that is L=L(q,q',t),but this term won't affect us to use the Euler-Lagrange equation
 
  • #3


I am happy to provide a response to your question about the Lagrangian for a rheonomic constraint. A rheonomic constraint is a constraint that depends on time, and it can be represented mathematically by a function of the generalized coordinates and time. In terms of the Lagrangian, this means that the constraint will appear as an additional term in the Lagrangian function.

When dealing with a system with a rheonomic constraint, the Lagrangian will indeed change. The additional term representing the constraint will be added to the original Lagrangian, and this will affect the equations of motion derived from the Euler-Lagrange equation.

In terms of the treatment of time, it is important to include it as a generalized coordinate in the Lagrangian. This is because the rheonomic constraint is dependent on time, and therefore, it must be included in the equations of motion. Ignoring time and using the Euler-Lagrange equation normally would not yield accurate results.

In summary, when dealing with a system with a rheonomic constraint, the Lagrangian will change due to the inclusion of the constraint term. Time should also be treated as a generalized coordinate in the Lagrangian to accurately account for the rheonomic constraint. I hope this helps clarify your understanding of the Lagrangian for a rheonomic constraint.
 

1. What is the Lagrangian for a rheonomic constraint?

The Lagrangian for a rheonomic constraint is a mathematical function that describes the dynamics of a system subject to a constraint, such as a fixed length rod or a rolling wheel. It is based on the principle of virtual work and is used to derive the equations of motion for the system.

2. How is the Lagrangian for a rheonomic constraint different from a regular Lagrangian?

The Lagrangian for a rheonomic constraint takes into account the constraints placed on the system, whereas a regular Lagrangian does not. This allows for a more accurate description of the system's dynamics, as it takes into consideration the constraints that must be satisfied.

3. Can the Lagrangian for a rheonomic constraint be used for any type of constraint?

Yes, the Lagrangian for a rheonomic constraint can be used for any type of constraint as long as it can be expressed mathematically. This includes constraints such as fixed lengths, rolling without slipping, and holonomic constraints.

4. How is the Lagrangian for a rheonomic constraint derived?

The Lagrangian for a rheonomic constraint is derived using the method of Lagrange multipliers. This involves adding terms to the regular Lagrangian to account for the constraints, and then using the Euler-Lagrange equations to find the equations of motion.

5. Can the Lagrangian for a rheonomic constraint be used for systems with multiple constraints?

Yes, the Lagrangian for a rheonomic constraint can be used for systems with multiple constraints. In this case, additional Lagrange multiplier terms are added to the Lagrangian to account for each constraint, and the resulting equations of motion will include all of the constraints.

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