Armenia Physics Unified Exam key terms

A vector pointing from an object's starting position to its final position; its magnitude is the straight-line distance between those points, and its direction matters, unlike total path length.

The rate at which displacement changes with time; a vector quantity whose direction is the direction of motion and whose magnitude is the object's speed along a straight path.

The rate at which velocity changes with time, including changes in speed, in direction, or both; it is a vector measured in metres per second squared.

Motion of a body under gravity alone, with air resistance neglected; near Earth's surface the acceleration is about 9.8 m/s² downward regardless of the body's mass.

Motion of an object launched into the air, analysed as independent horizontal motion at constant velocity and vertical motion with constant downward acceleration due to gravity.

The net force on a body equals the product of its mass and its acceleration; expressed as a vector equation, it links cause (force) to effect (change of motion).

The tendency of a body to resist changes in its state of motion; it is measured by mass, so a more massive body needs a larger force for the same acceleration.

The single vector sum of all forces acting on a body; it determines the body's acceleration, and when it is zero the body stays at rest or moves uniformly.

The state of a body when the vector sum of all forces and the sum of all torques acting on it are both zero, so it remains at rest or moves with constant velocity.

A measure of how strongly a force tends to rotate a body about an axis; it equals force times the perpendicular distance from the axis to the force's line of action.

The perpendicular distance between the axis of rotation and the line along which a force acts; multiplying force by this distance gives the torque produced.

The product of a body's mass and its velocity; a vector quantity that is conserved in collisions when no external force acts on the system.

The product of an average force and the time interval over which it acts; it equals the change in momentum produced by that force.

In an isolated system, the total vector momentum stays constant over time; this principle lets us analyse collisions and explosions without tracking every internal force.

Energy transferred to or from a body by a force acting through a displacement; it equals the force component along the displacement times the displacement length.

The energy a body possesses because of its motion; it equals half the mass times the square of the speed and is always non-negative for a given reference frame.

The total energy of an isolated system remains constant; energy may change form between kinetic, potential, thermal and other types, but the total amount is unchanged.

Energy stored in a system because of the relative positions of its parts or because of its configuration in a field, such as a raised mass or a stretched spring.

The rate at which work is done or energy is transferred; it equals work divided by the time taken, measured in watts, where one watt is one joule per second.

The ratio of useful energy or power output to total energy or power input, often expressed as a percentage; it is always less than one for real machines.

Temperature measured on the Kelvin scale, starting at absolute zero; it is used in gas laws and relates to average molecular kinetic energy, unlike Celsius or Fahrenheit readings.

A model gas whose molecules are treated as point particles with no attraction between them, colliding elastically; its pressure, volume and temperature obey a simple relationship.

The total kinetic and potential energy of the particles making up a system, excluding energy due to the system's overall motion or its position in external fields.

The change in a system's internal energy equals the heat added to it minus the work it does on its surroundings; a statement of energy conservation for thermal processes.

Energy transferred between bodies or a body and its surroundings because of a temperature difference; it is not a quantity stored inside a body.

The amount of heat needed to raise the temperature of one kilogram of a substance by one kelvin, measured in joules per kilogram per kelvin.

The heat absorbed or released by a substance during a change of state at constant temperature, such as melting or boiling, without any change in temperature.

A region around a charged object where another charge experiences an electric force; its strength at a point is the force per unit positive charge placed there.

The electric force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them, acting along the line joining them.

The electric potential energy per unit positive charge at a point in an electric field; the potential difference between two points drives current through a conductor.

The potential difference between two points in a circuit, equal to the work done per unit charge moving between them; it is measured in volts.

A measure of how strongly a component opposes the flow of electric current; it equals voltage across the component divided by the current through it, in ohms.

For a conductor at constant temperature, the current through it is directly proportional to the voltage across it, so the ratio of voltage to current stays constant.

A region around a magnet or moving charge where magnetic forces act on other moving charges or magnetic materials; its direction at a point is the direction a compass needle points.

The production of a voltage in a conductor when the magnetic flux through it changes, for example when a magnet moves near a coil or the coil rotates in a field.

The induced voltage in a loop equals the negative rate of change of magnetic flux through it; the minus sign expresses the direction given by Lenz's law.

The time taken for one complete cycle of an oscillation or wave, measured in seconds; it is the reciprocal of frequency.

The number of complete oscillations or wave cycles passing a point each second, measured in hertz; it is the reciprocal of the period.

The maximum displacement of an oscillating particle or wave from its equilibrium position; it relates to the energy carried by the oscillation.

A large increase in the amplitude of forced oscillations that occurs when the driving frequency matches a system's natural frequency, often leading to strong energy transfer.

The distance between two consecutive corresponding points on a wave, such as from crest to crest; it equals wave speed divided by frequency.

The change in direction of a wave as it passes from one medium into another where its speed differs, caused by the change in wave speed at the boundary.

Complete reflection of light back into a denser medium when it strikes a boundary at an angle greater than the critical angle, so no light leaves the medium.

The superposition of two or more waves meeting at a point, producing reinforcement where crests align and cancellation where a crest meets a trough.

The spreading of waves around obstacles and through openings, becoming noticeable when the obstacle or gap is comparable in size to the wavelength.

The emission of electrons from a metal surface when light of sufficiently high frequency falls on it; the effect reveals that light delivers energy in discrete packets.

A quantum of electromagnetic radiation carrying energy proportional to its frequency; it behaves as a particle when interacting with matter, as in the photoelectric effect.

The minimum energy needed to remove an electron from the surface of a particular metal; light below the corresponding frequency cannot cause photoelectric emission.

The time required for half of the radioactive nuclei in a sample to decay; it is a fixed characteristic of each isotope and is unaffected by temperature or pressure.

The spontaneous transformation of unstable atomic nuclei into other nuclei, emitting alpha particles, beta particles or gamma rays, with a characteristic probability per unit time.

The number of radioactive decays occurring in a sample per unit time, measured in becquerels; it decreases over time according to the isotope's half-life.

The estimated range within which the true value of a measured quantity is expected to lie, reflecting limitations of the instrument and the measurement procedure.

Measurement scatter that varies unpredictably between repeated readings, some too high and some too low; averaging repeated measurements reduces its effect on the result.

A consistent deviation of measurements from the true value in one direction, caused by a faulty instrument or flawed method; repeating readings does not reduce it.

The digits in a measured value that carry meaningful information about its precision; a result should be reported with no more of them than the least precise input allows.

The slope of a graph line, found as the change in the vertical quantity divided by the change in the horizontal quantity; it often equals a physically meaningful rate or constant.

Rearranging a relationship so that plotting the data gives a straight line, whose gradient and intercept then reveal the constants in the physical equation.