What is the Definition of p_Θ in Polar Coordinates?

  • Thread starter Thread starter td21
  • Start date Start date
  • Tags Tags
    Definition
Click For Summary
SUMMARY

The definition of p_Θ in polar coordinates relates to the conjugate momentum associated with the angular coordinate θ. The correct formulation is derived from the Lagrangian in Cartesian coordinates, transformed into spherical coordinates. The incorrect attempts at defining p_Θ as either m*(r*d/dt(θ))^2 or m*(d/dt(θ))^2 highlight a misunderstanding of the concept, as these expressions are quadratic in the angular velocity and do not represent conjugate momentum accurately.

PREREQUISITES
  • Understanding of Lagrangian mechanics
  • Familiarity with polar and spherical coordinate systems
  • Knowledge of conjugate momentum definitions
  • Basic principles of classical mechanics
NEXT STEPS
  • Study the derivation of the Lagrangian in Cartesian coordinates
  • Learn about the transformation of Lagrangians to polar coordinates
  • Research the definition and calculation of conjugate momentum in mechanics
  • Explore examples of momentum in spherical coordinates
USEFUL FOR

Students of physics, particularly those studying classical mechanics, as well as educators and anyone seeking to understand the application of polar coordinates in Lagrangian mechanics.

td21
Gold Member
Messages
177
Reaction score
8

Homework Statement


What is the definition of p_Θ?


Homework Equations


I search all over the web using the keyword linear "momentum polar coordinates", "lagrangian in polar coordinates", "hamiltonian in polar coordinates", "momentum in 2D polar coordinates" for about half an hour.
but i fail to find it.

The Attempt at a Solution


I think it is either:
1. p_Θ = m*(r*d/dt(θ))^2
2. p_Θ = m*(d/dt(θ))^2

which one is correct? Thank you!
 
Physics news on Phys.org
##p_\theta## is whatever the author of the context defines it to be. Without a bit more of that context it is impossible to help you.

I find it very hard to believe you were given an exercise for which the full problem statement is actually
What is the definition of p_Θ?

Your relevant equations are not equations at all and how long you searched for them is not relevant

Neither 1 nor 2 is correct in your attempt at a solution. Is my bet.

Please start over. I do want to help, even if this reply seems a bit sour...
 
*If* you are trying to find the conjugate momentum related to the angle ##\theta## in spherical coordinates for a point mass - this is not at all clear from your post - then your alternatives cannot be right as they are quadratic in ##\dot\theta##. I suggest you start from the Lagrangian in cartesian coordinates, transform it to spherical, and use the definition of the conjugate momentum.
 

Similar threads

Replies
8
Views
2K
Replies
15
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 9 ·
Replies
9
Views
7K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 12 ·
Replies
12
Views
4K
  • · Replies 2 ·
Replies
2
Views
4K
Replies
4
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K