Is action-reaction contained in the Lagrangian

  • Thread starter aaaa202
  • Start date
  • #1
1,170
3
A lot of conservation laws are derived from the lagrangian in my book. However, I fail to see why the Lagrangian incorporates action-reaction. Since it works for an arbitrary amount of particles and linear momentum can be show to be conserved from translational invariance it must do so.
But deriving it from the principle of stationary action, doesn't really have any assumption that action must have a reaction as far as I can see it.
What do I fail to see?
 

Answers and Replies

  • #2
35,401
11,767
With some assumptions about the shape of the Lagrangian and in classical physics, it can be shown similar to that.

In the general case, you do not have a conserved total momentum - just look at a pendulum as example.
 

Related Threads on Is action-reaction contained in the Lagrangian

  • Last Post
Replies
6
Views
2K
Replies
107
Views
18K
  • Last Post
Replies
4
Views
3K
Replies
21
Views
13K
  • Last Post
Replies
19
Views
920
  • Last Post
Replies
8
Views
3K
Replies
6
Views
1K
Replies
3
Views
3K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
13
Views
163
Top