- #1

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Firstly, I'm not sure where this equation comes from:

[tex]M_z=\sum_a \frac{\partial L}{\partial \dot{\phi}_a}[/tex]

and from that, how do you get

[tex]M_z=\sum_a m_a(x_a \dot{y}_a-y_a \dot{x}_a)[/tex]

Thanks for any help.

- Thread starter Piano man
- Start date

- #1

- 75

- 0

Firstly, I'm not sure where this equation comes from:

[tex]M_z=\sum_a \frac{\partial L}{\partial \dot{\phi}_a}[/tex]

and from that, how do you get

[tex]M_z=\sum_a m_a(x_a \dot{y}_a-y_a \dot{x}_a)[/tex]

Thanks for any help.

- #2

Meir Achuz

Science Advisor

Homework Helper

Gold Member

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The second equation comes from a change of variables from r,phi to x,y.

You may want to study the Lagrangian in a good mechanics book.

- #3

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When you say 'canonical momentum', is that derived from somewhere or is it empirical?

And I've been trying to change the variables to get the second equation, but I'm not getting anywhere. How does it work?

Thanks for your help.

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