Conservation law
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. The exact conservation laws include: conserv...
Ballistic Pendulums Are As Awesome As They Sound
How does a ballistic pendulum give information about a bullet or ball? Here is a derivation of the classic introductory physics problem. ALTHOUGH IT’S NOT always so simple to set up, a ballistic pendu...
(−1)F
In a quantum field theory with fermions, (−1) is a unitary, Hermitian, involutive operator where F is the fermion number operator and is equal to the sum of the lepton number plus the baryon number, F...
Ballistic Pendulums Are As Awesome As They Sound
How does a ballistic pendulum give information about a bullet or ball? Here is a derivation of the classic introductory physics problem. ALTHOUGH IT’S NOT always so simple to set up, a ballistic pendu...
Introduction to angular momentum
A video demonstration of angular momentumIn physics, angular momentum is the rotational counterpart of linear momentum. A freely-rotating disk (like a Frisbee in flight or a tire rolling down a hill...
Introduction to angular momentum - Wikipedia
Conserved current
In physics a conserved current is a current, , that satisfies the continuity equation . The continuity equation represents a conservation law, hence the name.Indeed, integrating the continuity equatio...
Conservation of mass
The law of conservation of mass, or principle of mass conservation, states that for any system closed to all transfers of matter and energy (both of which have mass), the mass of the system must remai...
Kirchhoff's circuit laws
Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits. They were first describ...
Kirchhoff's circuit laws - Wikipedia
Inversion transformation
In mathematical physics, inversion transformations are a natural extension of Poincaré transformations to include all conformal one-to-one transformations on coordinate space-time. They are less studi...
First law of thermodynamics
The first law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic systems. The law of conservation of energy states that the total energy of an isolated syst...
Color charge
Color charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD). The color charge of quarks and gluons is completely...
Color charge - Wikipedia
Continuity equation
A continuity equation in physics is an equation that describes the transport of a conserved quantity. Since mass, energy, momentum, electric charge and other natural quantities are conserved unde...
Translational symmetry
In geometry, a translation "slides" a thing by a: Ta(p) = p + a.In physics and mathematics, continuous translational symmetry is the invariance of a system of equations under any translation. Discrete...
Baryogenesis
In physical cosmology, baryogenesis is the generic term for the hypothetical physical processes that produced an asymmetry (imbalance) between baryons and antibaryons produced in the very early univer...
Derivation of the Navier-Stokes equations
The intent of this article is to highlight the important points of the derivation of the Navier–Stokes equations as well as the application and formulation for different families of fluids.
The Na...
Invariant (physics)
In mathematics and theoretical physics, an invariant is a property of a system which remains unchanged under some transformation.Note: Invariance, does not imply not varying, it pertains to a conditio...
Momentum
In classical mechanics, linear momentum or translational momentum (pl. momenta; SI unit kg m/s, or equivalently, N s) is the product of the mass and velocity of an object. For example, a hea...
Momentum - Wikipedia
Charge conservation
In physics, charge conservation is the principle that electric charge can neither be created nor destroyed. The net quantity of electric charge, the amount of positive charge minus the amount of nega...
Vis-viva equation
In astrodynamics, the vis-viva equation, also referred to as orbital-energy-invariance law, is one of the equations that model the motion of orbiting bodies. It is the direct result of the law of cons...
Local symmetry
In physics, a local symmetry is symmetry of some physical quantity, which smoothly depends on the point of the base manifold. Such quantities can be for example an observable, a tensor or the Lagrangi...
Noether's second theorem
In mathematics and theoretical physics, Noether's second theorem relates symmetries of an action functional with a system of differential equations. The action S of a physical system is an integral o...
Conservation of energy
Prof. Walter Lewin demonstrates the conservation of mechanical energy, touching a wrecking ball with his jaw. (MIT Course 8.01)In physics, the law of conservation of energy states that the total ene...
Conservation of energy - Wikipedia
Constant of motion
In mechanics, a constant of motion is a quantity that is conserved throughout the motion, imposing in effect a constraint on the motion. However, it is a mathematical constraint, the natural conseque...
Mass in general relativity
The concept of mass in general relativity (GR) is more complex than the concept of mass in special relativity. In fact, general relativity does not offer a single definition of the term mass, but offe...
Symmetry (physics)
In physics, a symmetry of a physical system is a physical or mathematical feature of the system (observed or intrinsic) that is preserved or remains unchanged under some transformation.A family of par...
Particle physics and representation theory
There is a natural connection between particle physics and representation theory, as first noted in the 1930s by Eugene Wigner. It links the properties of elementary particles to the structure of Lie ...
Particle physics and representation theory - Wikipedia
Noether's theorem
Noether's (first) theorem states that any differentiable symmetry of the action of a physical system has a corresponding conservation law. The theorem was proved by German mathematician Emmy Noether i...
Momentum operator
In quantum mechanics, momentum (like all other physical variables) is defined as an operator, which "acts on" or pre-multiplies the wave function ψ(r, t) to extract the momentum eigenvalue from the wa...