What is Conservation laws: Definition and 113 Discussions
In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves over time. Exact conservation laws include conservation of energy, conservation of linear momentum, conservation of angular momentum, and conservation of electric charge. There are also many approximate conservation laws, which apply to such quantities as mass, parity, lepton number, baryon number, strangeness, hypercharge, etc. These quantities are conserved in certain classes of physics processes, but not in all.
A local conservation law is usually expressed mathematically as a continuity equation, a partial differential equation which gives a relation between the amount of the quantity and the "transport" of that quantity. It states that the amount of the conserved quantity at a point or within a volume can only change by the amount of the quantity which flows in or out of the volume.
From Noether's theorem, each conservation law is associated with a symmetry in the underlying physics.
Homework Statement
Given the energy-momentum tensor for a perfect fluid, what is the conservation laws that I can compute from
\nabla_b T^{ab}=0
in a curve space-time.
Homework Equations
T^{ab}=(\rho + p) u^a u^b - p g^{ab}
where p is the pressure and \rho is the...
Globalization makes that we can become aware of what other physicists, located at different remote places, have achieved.
Kard1,2 is the author of the derivations of the fundamental equations of relativistic dynamics without using conservation laws. He starts by defining the momentum of a...
Homework Statement
A claim has been made that an electron decays into 2 neutrinos traveling in different directions. Which conservation laws would be violated by this decay and which would be obeyed?
Homework Equations
Momentum: p = mv
Mass-energy: E = mc²
Electron
Baryon number: 0...
Having a difficult time determining which laws and equations to use?
A 15.0 kg block is attached to a very light horizontal spring of force constant 350 N/m and is resting on a smooth horizontal table. Suddenly it is struck by a 3.00 kg stone traveling horizontally at 8.00m/s to the right...
Here's the question:
"An astronnaut working with many tools some distance away from a spacecraft is stranded when the "manueving unit" malfunctions. How can the astronaut return to the spacecraft by sacrificing some of the tools?"
I don't quite understand what they're getting at here...
I have read that in classical physics, symmetry under tranlsation implies conservation of linear momentum, and that symmetry under rotation implies conservation of angular momentum. Could you guys give me a brief explanation, or if the explanation is not brief Point me towards a good website...
Hi,
I am working on a simulation and I have a problem of similar nature to the following:
Consider a horizontal frictionless pipe containing two damped springs with the same diameter as the pipe. Suppose both of the springs are moving horizontally through the pipe, one faster than the...
The question I'm doing for homework that I can't get is...
A spring is compressed 10.0 cm by an average force of 50.0 N. If the spring shoots a 20.0 g pebble straight up into the air, how high will it rise?
It would be sooper awesome if you could help with this![COLOR=DarkSlateBlue]
This is probably a complete quack of an idea, but I can't get it out of my mind. I can't tell if it belongs more on an economics board, though. :bugeye:
Could conservation laws exist for quantities which are not tangible?
We all know there are laws like conservation of momentum...
Hi, I'm having a few problems with my Homework I'll post one question for now then if I find out where I got stuck I'll go on to my next question. Alright...
"A 1500kg car accelerates up a hill in an attempt to pass a semi truck, it had an initial velocity of 12m/s if accelerated at a rate...
I have a question about the Dirac field. If as quantum field theory states , every point in the Universe is filled with "virtual" photons , and if these "virtual" photons in turn give rise to electron-positron pairs , which being components of matter and anti-matter collide and annihilate each...
Anyone know what quantity is conserved if the Hamiltonian (classical) is invariant under a Galilean boost? Also how would I prove that it is this quantity that is conserved?
Cheers,
Norm