Independent variables of the Lagrangian

In summary, the conversation discusses the treatment of y and y' as independent variables, despite not actually being independent. The discussion also explores the possibility of binding velocities instead of positions. The linked discussion offers various explanations for why calculus of variations works, with one suggesting that y and y' are treated as independent algebraically.
  • #1
JanEnClaesen
59
4
Why are y and y' treated as independent variables, while they are not?

Another slightly related question:
if ' = d/dt then df'/dg' = df/dg because f' = df/dg g', but if we differentiate f' to g' we implicitly assume that df/dg is independent of g', is it?
 
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  • #2
Perhaps because y and y' are the values of y and y' at the boundaries of a path, in which case they do seem independent.
Hence a natural follow-up question, instead of binding the positions, why don't we bind the velocities?
 

Related to Independent variables of the Lagrangian

1. What is an independent variable in the Lagrangian?

An independent variable in the Lagrangian is a variable that is not affected by other variables and is used to describe the system being studied. It is typically denoted as q in the Lagrangian equation.

2. How are independent variables determined in the Lagrangian?

Independent variables in the Lagrangian are determined based on the physical parameters that are relevant to the system being studied. They can also be chosen based on mathematical convenience to simplify the equations of motion.

3. Can there be more than one independent variable in the Lagrangian?

Yes, there can be multiple independent variables in the Lagrangian. This is common in systems with multiple degrees of freedom, where each variable represents a different aspect of the system.

4. How do independent variables affect the Lagrangian equations?

The independent variables in the Lagrangian determine the form of the equations of motion and how the system evolves over time. They also dictate the boundary conditions and constraints of the system.

5. What is the role of independent variables in the Lagrangian formalism?

In the Lagrangian formalism, the independent variables are crucial in describing the dynamics of a system. They allow for a more general and elegant approach to solving problems in mechanics and physics.

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