GTLE Subject Specialism Physics key terms

The straight-line vector from an object's starting point to its current position, including direction. Unlike distance travelled, it depends only on the endpoints, so a round trip returns to zero.

The rate at which displacement changes with time, a vector quantity with both magnitude and direction. Average velocity divides total displacement by elapsed time; instantaneous velocity is its value at one moment.

The rate at which velocity changes with time, including changes in speed, direction, or both. It is a vector measured in metres per second squared and can be negative when opposing motion.

Motion under gravity alone, with air resistance ignored, so every object near Earth accelerates downward at about 9.8 metres per second squared regardless of mass. Horizontal and vertical components are treated independently.

Two-dimensional motion of an object launched into the air, where horizontal velocity stays constant and vertical motion accelerates at g. The parabolic path results from combining these independent components.

The net force on an object equals its mass times its acceleration, written F = ma. It links cause (resultant force) to effect (change in motion) and underlies nearly all dynamics problems.

A sketch showing one object in isolation with every external force drawn as an arrow from its point of application. Used to find the resultant force before applying Newton's laws.

A contact force opposing relative sliding or the tendency to slide between surfaces. Static friction adjusts up to a maximum; kinetic friction stays roughly constant once sliding begins.

The perpendicular contact force a surface exerts on an object resting against it. Its size adjusts to the situation and is not always equal to weight, for example on an incline or in a lift.

The product of an object's mass and velocity, a vector measured in kilogram metres per second. In a closed system the total momentum before and after a collision is unchanged.

In any system with no external resultant force, total momentum stays constant through collisions and explosions. This principle lets you solve collision problems without knowing the forces involved.

The product of a force and the time over which it acts, equal to the change in momentum. Extending contact time, as with crumple zones, reduces the peak force for the same momentum change.

A scalar has magnitude only, such as mass or energy; a vector has magnitude and direction, such as force or velocity. Adding vectors requires resolving into perpendicular components.

Splitting a force into perpendicular components, usually horizontal and vertical or parallel and perpendicular to a slope, using trigonometry. This makes equilibrium and acceleration problems solvable with simple equations.

Oscillation where acceleration is proportional to displacement from equilibrium and directed toward it. Period is independent of amplitude, and displacement follows a sinusoidal curve over time.

A large amplitude response occurring when a driving frequency matches an object's natural frequency. It explains tuning, instrument tone and structural failures such as the Tacoma Narrows collapse.

Period is the time for one complete cycle, measured in seconds; frequency is the number of cycles per second, measured in hertz. They are reciprocals, so f equals one divided by T.

The distance a wave crest travels per second, given by speed equals frequency times wavelength. Speed depends on the medium, while frequency is set by the source and stays constant across boundaries.

A pattern formed when two identical waves travel in opposite directions and superpose, producing fixed nodes and antinodes. It underlies string and pipe harmonics used in music and measurement.

When two or more waves meet, the resultant displacement at each point is the algebraic sum of the individual displacements. This explains interference fringes, beats and the formation of standing waves.

The reinforcement or cancellation of waves from two coherent sources. Constructive interference gives bright or loud regions; destructive interference gives dark or quiet regions when path differences match half wavelengths.

The spreading of waves as they pass an obstacle or aperture, most noticeable when the gap is comparable to the wavelength. It sets limits on the resolution of optical instruments.

The change in direction of a wave crossing a boundary between media of different speeds, described by Snell's law. Light bends toward the normal entering a denser medium.

Complete reflection of a wave inside a medium when the incidence angle exceeds the critical angle. It occurs only going from denser to less dense media and enables optical fibres and reflecting prisms.

The smallest angle of incidence at which total internal reflection begins, found from sine of the critical angle equals the ratio of the two refractive indices. Beyond it no refracted ray emerges.

For a conductor at constant temperature, current is directly proportional to potential difference across it, giving V = IR. Components such as filament lamps and diodes do not obey it.

The opposition to current flow in a component, equal to potential difference divided by current and measured in ohms. It depends on material, length, cross-sectional area and temperature.

A property of a material describing how strongly it resists current, equal to resistance times area divided by length. Unlike resistance, it does not depend on the sample's size or shape.

In series, components share one path so current is the same and voltages add. In parallel, components share voltage and currents add, giving a smaller combined resistance.

The junction rule states current into a point equals current out; the loop rule states voltages around any closed loop sum to zero. Together they solve multi-loop circuits.

The energy per unit charge supplied by a source such as a cell, measured in volts. It differs from terminal potential difference because internal resistance causes a drop under load.

The resistance inside a power source that causes its terminal voltage to fall as current increases. It dissipates energy as heat and limits the maximum current a cell can deliver.

The generation of an electromotive force when magnetic flux through a circuit changes, described by Faraday's law. Lenz's law fixes the induced current direction to oppose the change.

The product of magnetic flux density and the area perpendicular to it, measured in webers. A change in flux, through movement or field change, induces an electromotive force.

An induced current flows in the direction that opposes the change producing it, a consequence of energy conservation. It explains why magnets falling through copper tubes slow dramatically.

The energy needed to raise one kilogram of a substance by one kelvin, measured in joules per kilogram kelvin. It explains why water heats and cools slowly compared with metals.

The energy absorbed or released when a substance changes state without changing temperature, such as melting or boiling. It breaks bonds between particles rather than increasing kinetic energy.

The total kinetic and potential energy of the particles in a system. Heating, working on, or changing the state of a system can all change its internal energy.

The relationship pressure times volume equals number of moles times the gas constant times absolute temperature. It combines Boyle's, Charles's and pressure laws and requires temperature in kelvin.

The model explaining gas behaviour through randomly moving particles whose collisions with walls create pressure. Average kinetic energy is proportional to absolute temperature, linking microscopic motion to macroscopic properties.

The lowest possible temperature, zero kelvin or about minus 273 degrees Celsius, where particle kinetic energy reaches its minimum. Gas volume and pressure extrapolate to zero here.

The emission of electrons from a metal surface when light of sufficient frequency strikes it. It proves light behaves as photons with energy proportional to frequency, not as a continuous wave.

The minimum energy needed to remove an electron from a metal surface. Incident photon energy must exceed it for emission, and the surplus becomes the electron's maximum kinetic energy.

A discrete packet of electromagnetic energy whose energy equals Planck's constant times frequency. Photons travel at light speed and have no rest mass.

The time for half the nuclei in a radioactive sample to decay. It is constant for a given isotope and allows prediction of remaining activity using exponential decay.

The spontaneous transformation of unstable nuclei emitting alpha, beta or gamma radiation. It is random per nucleus yet statistically predictable for large samples, unaffected by temperature or pressure.

The number of nuclear decays per second in a sample, measured in becquerels. It decreases exponentially with time and falls to half its initial value after one half-life.

The range within which a measured value probably lies, arising from instrument resolution and random variation. It is quoted with a unit and often as a percentage of the reading.

Precision means repeated readings cluster closely together; accuracy means they are close to the true value. A measurement can be precise but inaccurate if a systematic error shifts all readings.

Systematic errors shift all readings the same way, such as a zero error, and are reduced by calibration. Random errors scatter readings unpredictably and are reduced by averaging repeats.

The digits in a result that carry meaningful information about its precision. A final answer should not be quoted more precisely than the least precise measurement used.

Using the gradient and intercept of a straight-line graph to extract physical quantities. Plotting a linearised relationship turns equations such as T squared against length into measurable straight lines.

A straight line drawn through plotted data to show the overall trend, with points scattered evenly on both sides. Its gradient and intercept are used to calculate physical constants.

A relationship where one quantity changes by the same factor as another, giving a straight line through the origin. Inverse and inverse-square relationships produce characteristic curves.

A written judgement before practical work identifying hazards, who might be harmed, and the controls that reduce risk. It must be specific to the experiment rather than generic boilerplate.

The rules and habits that prevent harm in practical physics, including eye protection, safe electrical practice, handling radioactive sources at distance and correct disposal of broken glass.

Assessment used during learning to identify gaps and adjust teaching, such as questioning, mini whiteboards and exit tickets. It is low stakes and gives feedback rather than grades.

Assessment at the end of a unit or course that judges attainment against standards, such as an end-of-topic test or practical endorsement. Results are typically recorded and reported.

A stable, plausible but incorrect idea a learner holds, such as heavier objects falling faster. Misconceptions resist correction by explanation alone and need targeted diagnostic teaching.

A teaching strategy that presents evidence contradicting a learner's misconception, prompting them to revise their thinking. The surprise creates a need to resolve the discrepancy.