# Questions tagged [conservation-laws]

The statement that a property of a system does not change if the system is isolated.

2,515 questions
Filter by
Sorted by
Tagged with
26 views

### Why change in momentum in vertical motion in a projectile not zero? [closed]

My answer is $$mv\sqrt{2}$$. I neglected the change in x component and just subtracted the initial y component of momentum with the negative(Rule of Coordinate system) of the same and computed the ...
43 views

### Conservation of charge and quantisation of charge

How does the idea of conservation of charge relate to the quantisation of charge.
181 views

### What does Conservation of momentum mean in Quantum mechanics?

In quantum mechanics why do we say that momentum in conserved when different measurements on particle give different values of it ? For example in ground state of Harmonic oscillator I know that ...
65 views

### Conservation of angular momentum using symmetry properties

Goldstein pg 59 It can be shown that if a cyclic coordinate $q_{j}$ is such that $d q_{j}$ corresponds to a rotation of the system of particles around some axis, then the conservation of its ...
20 views

### Fully developed flow in cylinder coordinates

I have a flow that is: steady (time derivative is zero) fully developed in-compressible (constant density) no slip at the wall axis-symetric (theta derivative is zero) The configuration of the pipe ...
55 views

### Physical interpretation of Klein-Gordon Equation conserved charge

In the Klein-Gordon Equation the conserved charge is: $$\rho = \frac{i \hbar}{2m} (\psi^* \frac{\partial \psi}{\partial t} - \frac{\partial \psi^*}{\partial t} \psi)$$ rather than the conserved (...
93 views

The Device: Imagine a physical system involving two circular rings of distinct inner and outer radii, but equal in inertia. The smaller ring is superimposed inside the inner radius of the larger ring. ...
26 views

### Newton's Principia Naturalis: question on Corollary III?

I'm reading Newton's Principia Naturalis and have a question on Corollary III p86: The quantity of motion, which is collected by taking the sum of the motions directed towards the same parts, and ...
60 views

### Is momentum conserved in our current cosmological models?

The cosmological principle states that the universe, on large enough scales, is homogenous and isotropic. Noether's theorem says that space-translational invariance corresponds to conservation of ...
72 views

### Global conservation + Lorentz invariance = local conservation?

On the page 83 of "Quantum Field Theory Lectures of Sidney Coleman", Coleman showed an interesting example: It seems that global conservation law and local conservation law can be related. ...
68 views

### The principle of conservation of electric charge (or law of conservation of electric charge) $\iff \sum_{i=1}^n q_i=0$?

The principle of conservation of electric charge (or law of conservation of electric charge) affirms that: in a closed (isolated) system, which does not exchange any matter with the outside, the ...
15 views

### Change in angular velocity of an initially non-rotating spherical object after a collision

In the theoretical scenario below: Will the object rotate? My first thoughts on this were: The initial angular velocity is $0$. This means it does not have any angular momentum (right...?) and it ...
37 views

### Are there any fusion reactions that reduce the number of baryons?

In the simplest of fusion reactions, two hydrogen nuclei fuse to form deuterium. Besides deuterium, we get a positron and an electron neutrino out of it. The positron combines with the extra electron ...
41 views

### A situation where mass and energy are separately conserved?

I know that in a closed system mass+energy is always conserved. For example, in an exothermic reaction, some mass is converted to energy. Now, I'm looking for a situation where mass and energy are ...
37 views

### Problem similar to Feynman disk paradox. (violation of conservation of angular momentum)

I have a problem(paradox) similar to Feynman disk paradox. There is a example similar to Feynman disk paradox in Griffiths electrodynamics. Example 8.4 shows that the initial angular momentum of ...
3k views

### Why should momentum be conserved in special relativity?

This is more of a philosophical question than an actual physics question, but I don't see a clear reason why relativistic momentum, or energy for that matter, should be conserved. The equivalence ...
49 views

### If the light was slowing down universally could we detect it? What do we need? [duplicate]

Is there a way to detect it if light was slowing down universally, i.e. if speed of light $c$ in vacuum was getting smaller? Edit I was directed to this question. But I did not find the answer I ...
78 views

### Intuition behind torque, rotational inertia and angular momentum

I'm reading about conservation of linear momentum and angular momentum. I understand the idea that angular momentum should be thought of as the "rotational analogue" of linear momentum, just ...
63 views

391 views

### Proof of Newton's Third Law

Recently, I started thinking about how to prove or, at least, provide an intuitive explanation for why Newton's third law should be true, and I found this article: https://www.lockhaven.edu/~dsimanek/...
98 views

### What is the physical reasoning behind the generation of equal but opposite force (Newton's third law)?

When I apply a force on a body, it will apply a force on me (Newton's third law). But where does this force on me (i.e. equal but opposite force) generate from? Does it generate from within the body, ...
50 views

### What is the difference between objectivity and symmetry?

I encounter this question when reading a paper about continuum mechanics (Kumar and Parks, 2015, Proc.R.Soc.A. refer to eq.3.1 and eq.3.3) Speaking of the objectivity of strain energy density ${\psi}$,...
52 views