
Review of Short Phrases and Links 
This Review contains major "Momentum" related terms, short phrases and links grouped together in the form of Encyclopedia article.
Definitions
 Momentum is the Noether charge of translational invariance.
 Momentum is a vector.
 Momentum is a conserved quantity.
 Momentum is the product of the mass and the velocity of an object.
 Momentum is a conserved quantity in physics which is the product of the mass m and velocity v of an object.
 In modern (late 20th century) theoretical physics, angular momentum is described using a different formalism.
 Constant angular momentum is extremely useful when dealing with the orbits of planets and satellites, and also when analyzing the Bohr model of the atom.
 Angular momentum is important in physics because it is a conserved quantity: a system's angular momentum stays constant unless an external torque acts on it.
 In quantum mechanics, angular momentum is quantized  that is, it cannot vary continuously, but only in " quantum leaps " between certain allowed values.
 In quantum mechanics momentum is defined as an operator on the wave function.
 I can only take on a restricted range of values (integer or halfinteger), but the 'orientation' of the associated angular momentum is also quantized.
 Before the explosion, the total momentum of the system is zero since the cannon and the tennis ball located inside of it are both at rest.
 Thus, when a gun is fired, the final total momentum of the system (the gun and the bullet) is the vector sum of the momenta of these two objects.
 For example, the kinetic energy stored in a massive rotating object such as a flywheel is proportional to the square of the angular momentum.
 State that an elastic collision is one in which both momentum and kinetic energy are conserved.
 Angular momentum is an important concept in both physics and engineering, with numerous applications.
 The second term is the angular momentum that is the result of the particles spinning about their center of mass.
 It is the same angular momentum one would obtain if there were just one particle of mass M moving at velocity V located at the center of mass.
 By pulling in her arms, she reduces her moment of inertia, causing her to spin faster (by the conservation of angular momentum).
 Concepts such as mass, momentum, inertia, or elasticity, become therefore crucial in describing acoustic (as opposed to optic) wave processes.
 Elastic collisions conserve kinetic energy as well as total momentum before and after collision.
 As seen from the definition, the derived SI units of angular momentum are newton metre seconds (Nms or kgm 2 s 1).
 Inelastic collisions don't conserve kinetic energy, but total momentum before and after collision is conserved.
 Objects without a rest mass, such as photons, also carry momentum.
 This spin angular momentum comes in units of .
 Indeed for fermions the spin S and total angular momentum J are halfinteger.
 Because angular momentum is constant in the absence of external torques, the angular velocity (rotational speed) of the skater has to increase.
 For the case where the angular momentum is parallel to the angular velocity, the moment of inertia is simply a scalar.
 Answer: (a) The disk and ball's angular momentum is still constant, but (b) now the disk and ball's angular velocity decreases as time passes.
 The conservation of angular momentum is used extensively in analyzing what is called central force motion.
 As a consequence, the canonical angular momentum is not gauge invariant either.
 The sign convention for angular momentum is the same as that for angular velocity.
 This gyroscope remains upright while spinning due to its angular momentum.
 Angular momentum is a pseudovector quantity because it gains an additional sign flip under an improper rotation.
 Examples of vectors include displacement, velocity, electric field, momentum, force, and acceleration.
 Momentum The rate of acceleration of a security's price or volume.
 Angular momentum operators usually occur when solving a problem with spherical symmetry in spherical coordinates.
 Rotational symmetry of space is related to the conservation of angular momentum as an example of Noether's theorem.
 If an object is moving in any reference frame, then it has momentum in that frame.
 In quantum mechanics, position and momentum are conjugate variables.
 The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa.
 Lesson #28b Momentum One useful consequence of Newton's 3rd law is the conservation of momentum, as is shown by analyzing the recoil of a cannon.
 The angular momentum of a particle of mass m moving with velocity v at the instant when it is at a distance r from the fixed point is mrv.
 The magnitude of this vector is the final momentum of the isolated system.
 This phenomenon is demonstrated by Newton's cradle, one of the best known examples of conservation of momentum, a real life example of this special case.
 Linear momentum is a vector quantity, since it has a direction as well as a magnitude.
 Relationship between force (F), torque (), and momentum vectors (p and L) in a rotating system.
 If the ball acquires 50 units of forward momentum, then the cannon acquires 50 units of backwards momentum.
 In a closed system angular momentum is constant.
 Example: In a closed system, the charge, mass, total energy, linear momentum and angular momentum of the system are conserved.
 Notice that twice the areal velocity times mass equals angular momentum, just as linear velocity times mass is linear momentum, i.e.
 For interactions between black holes and normal matter, the conservation laws of massenergy, electric charge, linear momentum, and angular momentum, hold.
 It turns out that the best that one can do is to simultaneously measure both the angular momentum vector's magnitude and its component along one axis.
 Because of the cross product, L is a pseudovector perpendicular to both the radial vector r and the momentum vector p.
 The time derivative of angular momentum is called torque: For other senses of this word, see torque (disambiguation).
 Impulse momentum is also a large part of Chapter 6, the impulse of a force acting on an object is equal to the product the force and the change in time.
 In contrast, the second law states an unbalanced force acting on an object will result in the object's momentum changing over time.
 In classical mechanics, an impulse changes the momentum of an object, and has the same units and dimensions as momentum.
 The concept of momentum in classical mechanics was originated by a number of great thinkers and experimentalists.
 In classical mechanics, momentum ( pl.
 Rotations and Angular Momentum on the Classical Mechanics page of the website of John Baez, especially Questions 1 and 2.
 In an isolated system (one where external forces are absent) the total momentum will be constant: this is implied by Newton's first law of motion.
 In all types of collision if no external force is acting on the system of colliding bodies, the momentum will always be preserved.
 Angular momentum can also be calculated by multiplying the square of the displacement r, the mass of the particle and the angular velocity.
 Therefore, there are limits to what can be known or measured about a particle's angular momentum.
 When describing the motion of a charged particle in the presence of an electromagnetic field, the "kinetic momentum" p is not gauge invariant.
 In a charged particle the momentum gets a contribution from the electromagnetic field, and the angular momenta L and J change accordingly.
 Thus, the net force on a particle is equal to the rate change of momentum of the particle with time.
 In d dimensions, the angular momentum will satisfy the same commutation relations as the generators of the d dimensional rotation group SO(d).
 The diagram can serve as a useful mnemonic for remembering the above relations involving relativistic energy , invariant mass , and relativistic momentum .
 Momentum is conserved in an electrodynamic system (it may change from momentum in the fields to mechanical momentum of moving parts).
 Momentum has the special property that, in a closed system, it is always conserved, even in collisions and separations caused by explosive forces.
 The origin of the use of p for momentum is unclear.
 To the dummy pilot in the cockpit there is no change of momentum.
 Elastic Collisions When two bodies collide their total momentum is conserved unless external forces act on them.
 Massless objects such as photons also carry momentum.
 We can say that the particles exchange "virtual photons" which carry the transferred momentum.
 This is analogous to the way that special relativity "mixes" space and time into spacetime, and mass, momentum and energy into fourmomentum.
 So, momentum conservation can be philosophically stated as "nothing depends on location per se".
 In understanding conservation of momentum, the direction of the momentum is important.
 Newton's Third Law reduces to a simple statement about momentum conservation.
 All we did was in fact equating velocities in the elementary equation of conservation of momentum.
 This is a commonly encountered form of the angular momentum operator, though not the most general one.
 Even though photons (the particle aspect of light) have no mass, they still carry momentum.
 The classical definition of angular momentum as depends on six numbers: r x, r y, r z, p x, p y, and p z.
 Momentum depends on two thing, mass and velocity, but both have set masses, so it's up to you to change the velocities.
 IRV does not have momentum, but dissatisfaction with voting systems does,.Third parties, once educated, will support RV but not IRV and not approval and not Condorcet.
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