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Foot-pound (energy)
The foot-pound (ft·lbf), also written foot pound-force, is a British imperial and US customary unit of energy, defined as the work of one pound-force over one foot.
Footprint model (micrometeorology)
A footprint model estimates the upwind surface area, or source area, contributing to a turbulent flux measured at a point above the ground, most often at an eddy-covariance tower.
Foraminifera in paleoclimatology
Foraminifera in paleoclimatology is the study of foraminiferal shells in seafloor sediments, whose oxygen isotope, trace metal, and assemblage signatures reconstruct past ocean temperature, ice volume, and salinity.
Forbidden line
A forbidden line is an emission line from an atomic transition that violates electric-dipole selection rules, visible in rarefied astronomical gas such as nebulae and the solar corona.
Forbush decrease
A Forbush decrease is a short-term reduction in galactic cosmic rays at Earth caused by coronal mass ejections, named for physicist Scott Forbush, who reported it in 1937.
Force
Force, also called a force vector, is a push or pull on an object with a specific magnitude and direction; its SI unit is the newton (N).
Force between magnets
The force between magnets is the attraction or repulsion two permanent magnets exert on each other: like poles repel, opposite poles attract, and the force weakens sharply with distance.
Force carrier
A force carrier, also called an exchange particle, is an elementary particle whose exchange between matter particles transmits a fundamental force, such as the photon or gluon.
Force chain
A force chain is a quasi-linear arrangement of three or more grains in a granular material, such as sand, that carries more than the average contact force, forming the load-bearing skeleton transmitting stress.
Force Concept Inventory
The Force Concept Inventory (FCI) is a multiple-choice test measuring students' conceptual understanding of Newtonian mechanics, created by David Hestenes and colleagues at Arizona State University and published in 1992.
Force constant
The force constant, written k, is the second derivative of a bond's potential energy at equilibrium, measuring bond stiffness and setting its vibrational frequency in infrared spectroscopy.
Force field (chemistry)
In chemistry, a force field is the set of mathematical functions and fitted parameters describing a system's potential energy, used in molecular mechanics and molecular dynamics simulations.
Force field parameterization
Force field parameterization, also called ligand parameterization, is the process of fitting molecular mechanics parameters such as charges, bond lengths, and torsional barriers to quantum-mechanical or experimental reference data.
Force spectroscopy
Force spectroscopy is a family of single-molecule methods that apply controlled mechanical force to individual molecules, using optical tweezers, magnetic tweezers, and atomic force microscopy.
Force volume imaging
Force volume imaging is an atomic force microscopy mode that records a complete force-distance curve at every pixel, producing maps of Young's modulus, stiffness, and adhesion.
Force-free magnetic field
A force-free magnetic field is a magnetic field in which the Lorentz force vanishes, so current runs parallel to the field; it describes the solar corona and relaxed laboratory plasmas.
ForceBalance
ForceBalance is a free, open-source software package for systematic optimization of force fields, developed by Lee-Ping Wang's group at UC Davis and used to fit the TIP4P-FB water model and Open Force Field's Parsley and Sage.
Forced convection
Forced convection is heat transfer between a surface and a fluid moved by an external agent such as a fan, pump, or wind, giving higher heat transfer rates than natural convection.
Forced degradation
Forced degradation, also known as stress testing, is a pharmaceutical analysis method that exposes drugs to heat, hydrolysis, oxidation, and light to characterize degradation products and validate stability-indicating methods.
Forced Rayleigh scattering
Forced Rayleigh scattering, also known as forced Rayleigh light scattering, is an optical pump–probe method that measures diffusion and thermodiffusion from the decay of a laser-written grating.
Forced vibration
Forced vibration is the oscillation of a mechanical system under a continued external periodic driving force, producing resonance when the driving frequency matches the system's natural frequency.
Forcing (mathematics)
Forcing, also called the forcing method, is a technique in mathematical logic, devised by Paul Cohen in 1963, for proving independence results in set theory.
Ford–Fulkerson algorithm
The Ford–Fulkerson algorithm, also called the Ford–Fulkerson method, computes maximum flow in a network by repeatedly augmenting along paths; it was proposed in 1956 by Ford and Fulkerson.
Forearc
A forearc is the region of a subduction zone between the ocean trench and the volcanic arc, hosting the shallow megathrust where the largest earthquakes nucleate.
Forecasting
Forecasting, also known as statistical forecasting, is the process of estimating a future value or state, like tomorrow's weather or demand, using historical data and structured methods.
Foreland basin
A foreland basin is a sedimentary basin beside a mountain belt, formed when the range's weight bends the lithosphere into a trough; the term was introduced in 1974.
Foreshock (plasma physics)
In plasma physics, a foreshock is the region upstream of a collisionless shock wave that is populated by particles reflected or leaked from the shock, streaming back upstream.
Forest plot
A forest plot, also known as a blobbogram, is a graphical display used in meta-analysis that shows each study's effect estimate and confidence interval alongside the pooled estimate.
Forest Ray Moulton
Forest Ray Moulton (1872–1952) was an American theoretical astronomer and celestial mechanician who co-developed the planetesimal hypothesis of the solar system's origin with geologist Thomas Chamberlin.
Forking (model theory)
Forking is a dependence relation on types in model theory, introduced by Saharon Shelah, whose negation, non-forking, serves as an abstract independence relation generalizing linear and algebraic independence.