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How many conservation laws ?

by bksree
Tags: conservation, laws
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bksree
#1
May8-11, 02:10 AM
P: 55
Hi
How many conservation laws are there ?
1. Conservation of energy
2. " " momentum
3. " mass
4. " charge
????


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Curl
#2
May8-11, 02:42 AM
P: 757
energy
momentum
angular momentum
charge
gravity
+ others I can't think of right now

mass conservation isn't really true
I like Serena
#3
May8-11, 03:18 AM
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color charge
weak isospin
probability density
CPT symmetry (combining charge, parity and time conjugation)
Lorentz symmetry

(ripped from http://en.wikipedia.org/wiki/Conservation_law)

Drakkith
#4
May8-11, 08:01 AM
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How many conservation laws ?

Quote Quote by Curl View Post
mass conservation isn't really true
Yeah, It all depends on what you mean by "mass". Converting electrons-positrons to gamma rays removes the "mass" and turns it into energy or momentum or whatever.
Vanadium 50
#5
May8-11, 09:39 AM
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I don't know what "conservation of gravity" even means. As for weak isospin, it is certainly not conserved, although it's third component is.

There is no answer to this question. What is conserved and what is not depends on the state you are looking at: an object in a central force orbit always has angular momentum conserved, but in a 1/r potential, it also has another quantity conserved: the Runge-Lenz vector.

Additionally, if x and y are conserved, x + ay is conserved as well, for all values of a. So if there are two, there are an infinite number.
Drakkith
#6
May8-11, 09:47 AM
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I think the OP was simply asking about the "Conservation Laws".

From wikipedia, it lists a few things seperated into "exact laws" and "approximate laws".
A partial listing of conservation laws that are said to be exact laws, or more precisely have never been shown to be violated:

Conservation of mass-energy
Conservation of linear momentum
Conservation of angular momentum
Conservation of electric charge
Conservation of color charge
Conservation of weak isospin
Conservation of probability density
CPT symmetry (combining charge, parity and time conjugation)
Lorentz symmetry

There are also approximate conservation laws. These are approximately true in particular situations, such as low speeds, short time scales, or certain interactions.

Conservation of mass (applies for non-relativistic speeds and when there are no nuclear reactions)
Conservation of baryon number (See chiral anomaly)
Conservation of lepton number (In the Standard Model)
Conservation of flavor (violated by the weak interaction)
Conservation of parity
Invariance under Charge conjugation
Invariance under time reversal
CP symmetry, the combination of charge and parity conjugation (equivalent to time reversal if CPT holds)
1MileCrash
#7
May8-11, 02:03 PM
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Quote Quote by Drakkith View Post
Yeah, It all depends on what you mean by "mass". Converting electrons-positrons to gamma rays removes the "mass" and turns it into energy or momentum or whatever.
Would it then be correct to say that a conservation of matter doesn't exist, but a conservation of mass does, seeing as energy does possess mass?
Drakkith
#8
May8-11, 02:29 PM
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Quote Quote by 1MileCrash View Post
Would it then be correct to say that a conservation of matter doesn't exist, but a conservation of mass does, seeing as energy does possess mass?
As wikipedia put it, I'd call it Conservation of mass-energy.
samuelarnold
#9
May9-11, 02:05 AM
P: 15
The concept of mass–energy equivalence connects the concepts of conservation of mass and conservation of energy, which continue to hold separately. The theory of relativity allows particles which have rest mass to be converted to other forms of mass which require motion, such as kinetic energy, heat, or light.From WkiPedia.


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