The quantity of motion. Linear momentum is the quantity obtained by multiplying the mass of a body by its linear speed. Angular momentum is the quantity obtained by multiplying the moment of inertia of a body by its angular speed.
Related Terms 
POPOV'S STABILITY CRITERION
A frequency domain stability test for systems consisting of a linear component described by a transfer function preceded by a nonlinear component characterized by an inputoutput function), with a unity gain feedback loop surrounding the series connection.

POLEPOSITIONING
A design technique used in linear control theory in which many or all of a system's closedloop poles are positioned as required, by proper choice of a linear state feedback law; if the system is controllable, all of the closedloop poles can be arbitrarily positioned by this technique.

PLASTICOVISCOSITY
Plasticity in which the rate of deformation of a body subjected to stresses greater than the yield stress is a linear function of the stress.

PIECEWISE LINEAR SYSTEM
A system for which one can divide the range of values of input quantities into a finite number of intervals such that the output quantity is a linear function of the input quantity within each of these intervals.

OPTIMAL SMOOTHER
An optimal filer 383 orbital angular momentum orbital moment of the position vector with the linear momentum. Also known as orbital momentum.

ONSAGER RECIPROCAL RELATIONS
A set of conditions which state that the matrix, whose elements express various fluxes of a system (such as diffusion and heat conduction) as linear functions of the various conjugate affinities (such as mass and temperature gradients) for systems close to equilibrium, is symmetric when certain definitions are chosen for these fluxes and affinities.

OFFLINE
1. A condition existing when the drive rod of the drill swivel head is not centered and parallel with the borehole being drilled. 2. A borehole that has deviated from its intended course. 3. A condition existing wherein any linear excavation (shaft, drift, borehole) deviates from a previously determined or intended survey line or course. 4. State in which an equipment or subsystem is in standby, maintenance, or mode of operation other than online.

OBSERVER
A linear system B driven by the inputs and outputs of another linear system A which produces an output that converges to some linear function of the state of system A. Also known as state estimator; state observer.

NORMAL ACCELERATION
1. The component of the linear acceleration of an aircraft or missile along its normal, or Z, axis. 2. The usual or typical acceleration.

NONMINIMUMPHASE SYSTEM
A linear system whose transfer function has one or more poles or zeros with positive, nonzero real parts.
