I Does Lagrangian Mechanics Handle Variable Mass System?

AI Thread Summary
Lagrangian mechanics can address variable mass systems, unlike Newtonian mechanics, which struggles due to the changing nature of the object's mass. The discussion highlights the challenges in defining an object with variable mass, particularly in relation to Newton's laws, which apply to constant mass systems. Critics argue that without a fixed mass, it becomes complex to formulate the second law of motion. The conversation also points out that many online sources misinterpret the treatment of variable mass systems, emphasizing the importance of accurate information. Understanding these principles is crucial for applications like rocketry, where mass changes significantly during operation.
Pikkugnome
Messages
23
Reaction score
6
How to handle a variable mass system with Lagrangian mechanics? As far as I understand Newtonian mechanics fails, because the object is not constant anymore, it is updated every moment to a new object with different physical properties. I don't immediately see how Lagrangian mechanics can do better.
 
Physics news on Phys.org
What makes you think Newtonian mechanics cannot handle variable mass systems? If that were the case it would be difficult to build a rocket to go to the Moon etc.
 
Reply
  • Like
Likes Vanadium 50 and vanhees71
The first and second law specifically talk about one object. I don't think it is possible to define an object on the fly so to speak as one wishes. What would be the form of the 2nd law, if the object itself was a variable?
 
Pikkugnome said:
The first and second law specifically talk about one object. I don't think it is possible to define an object on the fly so to speak as one wishes. What would be the form of the 2nd law, if the object itself was a variable?
A lot of Internet sources get wrong the treatment of a variable mass system. Not Wikipedia:

https://en.m.wikipedia.org/wiki/Variable-mass_system
 
Reply
  • Informative
  • Like
Likes vanhees71 and berkeman

Thread 'Derivation of Hamilton's Principle: Questions'

I have recently been really interested in the derivation of Hamiltons Principle. On my research I found that with the term ##m \cdot \frac{d}{dt} (\frac{dr}{dt} \cdot \delta r) = 0## (1) one may derivate ##\delta \int (T - V) dt = 0## (2). The derivation itself I understood quiet good, but what I don't understand is where the equation (1) came from, because in my research it was just given and not derived from anywhere. Does anybody know where (1) comes from or why from it the...
View full post »

Similar threads

I Checking if a stationary point is a minimum using Lagrangian Mechanics
Replies
1
Views
2K
The definition of generalised momentum
Replies
43
Views
4K
I Can Any Quantifiable Variable Serve as a Coordinate in Euler-Lagrange Equations?
Replies
5
Views
2K
I Using reference frames for derivation of Lagrangian
Replies
25
Views
2K
I Lagrangian symmetry for the bullet and gun
Replies
7
Views
1K
Insights How to Apply Newton’s Second Law to Variable Mass Systems
Replies
0
Views
2K
Lagrangian Mechanics: Variable Mass System?
Replies
2
Views
2K
Effective Potential in Lagrangian & Hamiltonian Mechanics
Replies
1
Views
3K
I Noether’s theorem -- Question about symmetry coordinate transformation
Replies
4
Views
1K
I How Does Landau Justify the Additivity of Lagrangians in Isolated Systems?
Replies
9
Views
2K

Hot Threads

Recent Insights

Back
Top