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Conservation law
 
 
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In physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
, a conservation law states that a particular measurable property of an isolated physical system
Physical system

In physics the word system has a technical meaning, namely, it is the portion of the physical universe chosen for analysis. Everything outside the system is known as the environment, which in analysis is ignored except for its effects on the system....
 does not change as the system evolves. Any particular conservation law is a mathematical identity to certain symmetry of a physical system
Symmetry in physics

Symmetry in physics includes all features of a physical system that exhibit the property of symmetry?that is, under certain transformation , aspects of these systems are "unchanged", according to a particular observation....
. A partial listing of conservation laws that are said to be exact laws, or more precisely have never been shown to be violated:

There are also approximate conservation laws.






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In physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
, a conservation law states that a particular measurable property of an isolated physical system
Physical system

In physics the word system has a technical meaning, namely, it is the portion of the physical universe chosen for analysis. Everything outside the system is known as the environment, which in analysis is ignored except for its effects on the system....
 does not change as the system evolves. Any particular conservation law is a mathematical identity to certain symmetry of a physical system
Symmetry in physics

Symmetry in physics includes all features of a physical system that exhibit the property of symmetry?that is, under certain transformation , aspects of these systems are "unchanged", according to a particular observation....
. 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 energy
    Conservation of energy

    The law of conservation of energy states that the total amount of energy in an isolated system remains constant. A consequence of this law is that energy cannot be created or destroyed....
  • Conservation of linear momentum
    Momentum

    In classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section Momentum#Modern definitions of momentum on this page....
  • Conservation of angular momentum
    Angular momentum

    In physics, the angular momentum of a particle about an origin is a vector quantity related to rotation, equal to the mass of the particle multiplied by the cross product of the position vector of the particle with its velocity vector....
  • Conservation of electric charge
    Electric charge

    Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields....
  • Conservation of color charge
    Color charge

    In particle physics, color charge is a property of quarks and gluons which are related to their strong interactions in the context of quantum chromodynamics ....
  • Conservation of weak isospin
    Weak isospin

    The weak isospin in particle physics is a quantum number relating to the weak interaction, and parallels the idea of isospin under the strong interaction....
  • Conservation of probability
    Continuity equation

    A continuity equation is a differential equation that describes the conservative transport of some kind of quantity. Since mass, energy, momentum, and other natural quantities are conserved, a vast variety of physics may be described with continuity equations....


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
    Conservation of mass

    The law of conservation of mass/matter, also known as law of mass/matter conservation says that the mass of a closed system will remain constant, regardless of the processes acting inside the system....
     (applies for low speeds)
  • Conservation of baryon number
    Baryon number

    In particle physics, the baryon number is an conservation laws quantum number of a system. It is defined as:whereWhy one third? According to the laws of strong interaction there cannot be any bare color charge, i.e....
     (See chiral anomaly
    Chiral anomaly

    A chiral anomaly is the anomaly nonconservation of a chirality current. In some theories of chiral fermion the quantization may lead to the breaking of this chiral symmetry....
    )
  • Conservation of lepton number
    Lepton number

    In high energy physics, the lepton number is the number of leptons minus the number of antileptons.In equation form,so all leptons have assigned a value of +1, antileptons −1, and non-leptonic particles 0....
     (In the Standard Model
    Standard Model

    The Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions....
    )
  • Conservation of flavor (violated by the weak interaction
    Weak interaction

    The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
    )
  • Conservation of parity
    Parity (physics)

    In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all spatial coordinates:...
  • CP symmetry


See also

  • Continuity equation
    Continuity equation

    A continuity equation is a differential equation that describes the conservative transport of some kind of quantity. Since mass, energy, momentum, and other natural quantities are conserved, a vast variety of physics may be described with continuity equations....
  • Noether's theorem
    Noether's theorem

    Noether's theorem states that any derivative Symmetry in physics of the action of a physical system has a corresponding conservation law. The action of a physical system is an integral of a so-called Lagrangian function, from which the system's behavior can be determined by the principle of least action....
  • Philosophy of physics
    Philosophy of physics

    In philosophy, the philosophy of physics studies the fundamental philosophy questions underlying modern physics, the study of matter and energy and how they interaction....
  • Symmetry in physics
    Symmetry in physics

    Symmetry in physics includes all features of a physical system that exhibit the property of symmetry?that is, under certain transformation , aspects of these systems are "unchanged", according to a particular observation....


External links

  • — an online textbook