# What is the physical meaning of momentum

## pulse

pulse, 1)non-relativistic mechanics: that as the product of mass m and speed v = dr / dt of a mass point defined vector p = mv.

It is r the position vector starting from any reference point 0 to the trajectory of the mass point. The amount p of impulse is also called Movement size. The momentum vector has the same direction as v and is therefore tangential to it at every point on the trajectory. In systems of mass points, the total momentum is equal to the sum of the individual momentum vectors. For a rigid body with density ρ and total volume V then the impulse results for any translational and rotational movement .

In it is the sum of the current translation speed u a fixed reference point and the speed of rotation of the respective mass element. All of these elements rotate with the common instantaneous angular velocity ω around a momentary axis of rotation passing through the reference point. The principle of conservation of momentum applies to the total momentum of the mass point system. The momentum of a mechanical system can be derived from its Lagrange functionL. or Hamilton function H certainly. With generalized coordinates qi result the generalized impulses too .

2)Electrodynamics: The concept of momentum can also be extended to physical fields. In the case of the electromagnetic field, the fact that every light wave carries an impulse with it, which is expressed in the pressure of light during the transmission of impulses on a surface, is represented by the impulse density of the electromagnetic field.

3)Special theory of relativity: The momentum of a particle with rest mass m0 is through given. (c is the speed of light in a vacuum.) Defined instead m0 a speed-dependent mass , so it simply applies p = mv, analogous to non-relativistic mechanics. The impulse forms together with the energy E. = pOc a four-vector whose four components (p0, p1, p2, p3) = m (c, vx, vy, vz) are. The temporal constancy of this four-vector is a statement that is independent of the reference system. According to Heisenberg's uncertainty principle of quantum mechanics, the momentum for microparticles such as electrons and protons cannot be measured simultaneously with the location with any precision.