NSSCAS Grade 12 Physics (Syllabus 8225): Comprehensive Practice Flashcards

Comprehensive vocabulary flashcards covering the full Namibia Senior Secondary Certificate Advanced Subsidiary (NSSCAS) Physics syllabus (Code 8225) and national examination papers, including General Physics, Kinematics, Dynamics, Forces & Pressure, Work, Energy & Power, Deformation of Solids, Waves & Superposition, Electricity & DC Circuits, and Nuclear/Fundamental Particle Physics.

Scalar Quantity

A physical quantity that has a numerical magnitude only, with no direction (for example, mass, time, temperature, and speed).

Vector Quantity

A physical quantity that possesses both a numerical magnitude and a direction (for example, displacement, velocity, acceleration, and force).

SI Base Quantities and Units

The six fundamental metric units specified in the syllabus: mass in kilograms ($\text{kg}$), length in metres ($\text{m}$), time in seconds ($\text{s}$), electric current in amperes ($\text{A}$), thermodynamic temperature in kelvin ($\text{K}$), and amount of substance in moles ($\text{mol}$).

Precision

The degree of agreement among independent measurements of the same quantity; precise measurements are all tightly grouped or close to one another.

Accuracy

The closeness of agreement between an individual measured value (or an average of values) and the true value of the quantity being measured.

Systematic Error

An error that causes readings to deviate constantly or predictably in one direction from the true value, including zero errors and calibration flaws.

Random Error

Unpredictable fluctuations in experimental conditions or observer judgement that cause measured values to scatter around a mean, reducible by averaging repeated readings.

Distance

A scalar measurement of the length of the path an object travels between two points, without consideration of direction.

Displacement

A vector quantity whose magnitude is the shortest distance between the initial and final positions, directed from the initial point to the final point.

Instantaneous Velocity

The rate of change of displacement with respect to time, or the speed of an object along a given direction at a specific instant.

Acceleration

The rate of change of velocity with respect to time ($a = \frac{\Delta v}{\Delta t}$), having SI base units of $\text{m}\,\text{s}^{-2}$.

Mass

The intrinsic property of a body that resists changes in its motion (its inertia).

Linear Momentum

The product of an object's mass and its velocity ($p = mv$), with the SI unit of $\text{N}\,\text{s}$ or base units $\text{kg}\,\text{m}\,\text{s}^{-1}$.

Force

The rate of change of linear momentum of a body ($F = \frac{\Delta p}{\Delta t}$), possessing the SI base units of $\text{kg}\,\text{m}\,\text{s}^{-2}$.

Newton's First Law of Motion

An object at rest remains at rest, or if moving continues to move at constant velocity in a straight line, unless acted on by a resultant force.

Newton's Second Law of Motion

The resultant force exerted on a body is directly proportional to the rate of change of linear momentum of that body ($\Sigma F = \frac{\Delta p}{\Delta t}$) and acts in the direction of the change.

Newton's Third Law of Motion

When two bodies interact, they exert forces on each other that are equal in magnitude, opposite in direction, and act on different bodies.

Weight

The force experienced by a mass due to the effect of a gravitational field, calculated as the product of mass and the acceleration of free fall ($W = mg$).

Terminal Velocity

The constant maximum velocity attained by a falling body when the resistive drag force in a fluid equals the downward gravitational force, resulting in zero net force and zero acceleration.

Impulse

The product of the resultant force acting on an object and the time duration for which it acts ($\text{Impulse} = F\Delta t$), which equals the change in linear momentum ($\Delta p$).

Principle of Conservation of Momentum

The principle stating that when bodies in a system interact, the total momentum remains constant provided that no external resultant force acts on the system.

Elastic Collision

A collision between bodies in which total kinetic energy is conserved and the relative speed of approach is equal to the relative speed of separation.

Inelastic Collision

A collision between bodies in which total momentum is conserved, but total kinetic energy is not conserved (some kinetic energy is transformed into internal, sound, or deformation energy).

Centre of Gravity

The single point through which the entire weight of a body may be considered to act.

Moment of a Force

The product of the applied force and the perpendicular distance from the pivot to the line of action of the force ($\text{Moment} = F \times d_{\perp}$), with SI base units of $\text{kg}\,\text{m}^2\,\text{s}^{-2}$.

Couple

A pair of forces of equal magnitude acting in opposite directions along parallel but distinct lines of action that tends to produce rotation only.

Torque of a Couple

The product of the magnitude of one of the forces in a couple and the perpendicular distance between the lines of action of the two forces.

Principle of Moments

For an object in rotational equilibrium, the sum of clockwise moments about any chosen pivot is equal to the sum of anticlockwise moments about the same pivot.

Equilibrium of Forces

The physical condition where both the resultant external force and the resultant external torque acting on a system are zero, resulting in zero linear and rotational acceleration.

Density

The mass per unit volume of a substance ($\rho = \frac{m}{V}$), measured in $\text{kg}\,\text{m}^{-3}$.

Pressure

The perpendicular force exerted per unit area of a surface ($p = \frac{F}{A}$), with the SI unit of pascal ($\text{Pa}$) or base units $\text{kg}\,\text{m}^{-1}\,\text{s}^{-2}$.

Work

The product of a force and displacement in the direction of that force ($W = Fs\cos(\theta)$).

Efficiency

The ratio (or percentage) of the useful energy output from a device or system to the total energy input ($\text{Efficiency} = \frac{\text{Useful energy output}}{\text{Total energy input}} \times 100\%$).

Gravitational Potential Energy

The energy possessed by a mass due to its position within a gravitational field, given near the Earth's surface by $\Delta E_p = mg\Delta h$.

Elastic Potential Energy

The strain energy stored in an object as a result of reversible (elastic) deformation, determined by the area under a force-extension graph ($E_p = \frac{1}{2}Fx = \frac{1}{2}kx^2$).

Power

The rate at which work is done or energy is transferred per unit time ($P = \frac{W}{t} = Fv$), measured in watts ($\text{W}$) with SI base units $\text{kg}\,\text{m}^2\,\text{s}^{-3}$.

Hooke's Law

The principle that the tensile or compressive extension of an elastic body is directly proportional to the applied load ($F = kx$), provided the limit of proportionality is not exceeded.

Spring Constant

The ratio of applied force to the resulting extension of an elastic component ($k = \frac{F}{x}$), expressed in $\text{N}\,\text{m}^{-1}$.

Stress

The internal force per unit cross-sectional area perpendicular to the applied force in a material ($\sigma = \frac{F}{A}$), measured in $\text{Pa}$ or $\text{N}\,\text{m}^{-2}$.

Strain

The ratio of the extension produced in a material to its original unstretched length ($\varepsilon = \frac{\Delta L}{L}$), which is a dimensionless quantity.

Young Modulus

The ratio of tensile stress to tensile strain for a material within its limit of proportionality ($E = \frac{\sigma}{\varepsilon}$), expressed in units of pascals ($\text{Pa}$).

Elastic Deformation

A change of shape or size of a material under load that is completely reversible, allowing the object to return to its original dimensions when the deforming force is removed.

Plastic Deformation

A permanent change of shape or size of a material occurring beyond its elastic limit as a result of atomic dislocations, such that it remains deformed after the load is removed.

Progressive Wave

A continuous oscillation that propagates through space or a medium, transferring energy from one place to another without any net movement of the medium itself.

Transverse Wave

A wave in which the particles of the medium or electromagnetic fields oscillate perpendicular to the direction of propagation of the wave's energy.

Longitudinal Wave

A wave in which the oscillations of the particles in the medium occur parallel to the direction of travel of the wave's energy, creating alternating compressions and rarefactions.

Wave Intensity

The radiant power transmitted per unit area perpendicular to the direction of propagation ($\text{Intensity} = \frac{\text{Power}}{\text{Area}}$), which is directly proportional to the square of the wave's amplitude ($I \propto A^2$).

Doppler Effect

The observed change in frequency (and wavelength) of a wave when the source of the waves moves relative to a stationary observer ($f_o = \frac{f_s v}{v \pm v_s}$).

Principle of Superposition

When two or more waves meet and overlap at a point, the resultant displacement at that point is equal to the algebraic (vector) sum of the displacements of each individual wave.

Stationary Wave

A wave pattern that traps and stores energy without transferring it forward, formed by the superposition of two progressive waves of equal frequency, wavelength, and amplitude travelling in opposite directions.

Node

A point along a stationary wave where destructive interference is complete, resulting in zero displacement and zero amplitude at all times.

Antinode

A point along a stationary wave where constructive interference occurs, producing maximum displacement and amplitude.

Diffraction

The spreading of waves around the edges of an obstacle or as they pass through an aperture, being most pronounced when the aperture width is comparable to the wavelength.

Coherence

The condition of two or more wave sources emitting waves that have the same frequency (and wavelength) and maintain a constant phase difference over time.

Interference

The effect produced when two or more coherent waves superpose, resulting in regions of constructive reinforcement (maxima) and destructive cancellation (minima).

Electric Field

A field of force representing a region in space in which an electric charge experiences an electrostatic force due to another charge.

Electric Field Strength

The electrostatic force experienced per unit positive point charge placed at that location in an electric field ($E = \frac{F}{Q}$), measured in $\text{N}\,\text{C}^{-1}$ or $\text{V}\,\text{m}^{-1}$.

Coulomb

The SI unit of electric charge, defined as the quantity of charge conveyed across a conductor cross-section in one second by a steady current of one ampere ($1\,\text{C} = 1\,\text{A}\,\text{s}$).

Electric Current

The net rate of flow of electric charge carriers through a conducting path ($I = \frac{\Delta Q}{\Delta t}$), expressed microscopically as $I = Anvq$.

Drift Velocity

The average net axial velocity with which mobile charge carriers drift along a conductor under the influence of an applied electric potential gradient ($v = \frac{I}{Anq}$).

Potential Difference

The energy transferred (work done) per unit electric charge from electrical energy to other non-electrical forms between two points in a circuit ($V = \frac{W}{Q}$).

Electromotive Force (e.m.f.)

The total energy transferred per unit charge from chemical or other non-electrical sources into electrical energy in driving charge through a complete closed circuit.

Volt

The SI unit of both electric potential difference and electromotive force, defined as the ratio of one joule of energy per coulomb of charge ($1\,\text{V} = 1\,\text{J}\,\text{C}^{-1}$).

Resistance

The opposition of a conductor to the flow of electric current, defined as the ratio of the potential difference across it to the current flowing through it ($R = \frac{V}{I}$).

Ohm

The SI unit of electrical resistance, defined as the resistance of a conductor transmitting a current of one ampere when subjected to a potential difference of one volt ($1\,\Omega = 1\,\text{V}\,\text{A}^{-1}$).

Ohm's Law

The principle that the current flowing through a metallic conductor is directly proportional to the potential difference across it, provided temperature and other physical conditions remain constant.

Resistivity

A material property defined as the product of electrical resistance and cross-sectional area per unit length of the specimen ($\rho = \frac{RA}{l}$), expressed in $\Omega\,\text{m}$.

Internal Resistance

The electrical resistance inherent within an electrical source of e.m.f. itself, which causes the terminal potential difference to fall below the e.m.f. when a current is drawn ($V = E - Ir$).

Kirchhoff's First Law

The principle of conservation of electric charge stating that the total current entering any electrical circuit junction is equal to the total current leaving that junction ($\Sigma I_{\text{in}} = \Sigma I_{\text{out}}$).

Kirchhoff's Second Law

The principle of conservation of energy stating that the algebraic sum of electromotive forces (e.m.f.s) around any closed loop in a circuit equals the sum of the potential differences around that loop ($\Sigma E = \Sigma IR$).

Potential Divider

A circuit consisting of two or more resistors connected in series across a voltage source to provide an output potential difference that is a predetermined fraction of the input voltage.

Radioactive Decay

The spontaneous and random emission of ionising particles and/or electromagnetic radiation from an unstable atomic nucleus.

Proton Number

The total number of protons present in the nucleus of an atom, denoted by the atomic number $Z$.

Nucleon Number

The total combined number of protons and neutrons contained in the nucleus of an atom, denoted by the mass number $A$.

Isotopes

Nuclides of the same chemical element having the same proton number ($Z$) but different numbers of neutrons ($N$).

Alpha Particle

A helium-4 nucleus consisting of two protons and two neutrons ($^4_2\alpha$ or $^4_2\text{He}^{2+}$) emitted during radioactive alpha decay, with a charge of $+2e$.

Beta-minus Decay

A nuclear decay process wherein an unstable neutron transforms into a proton, emitting a high-speed electron ($^0_{-1}\beta$) and an electron antineutrino ($\bar{\nu}_e$).

Beta-plus Decay

A nuclear decay process wherein an unstable proton transforms into a neutron, emitting a positron ($^0_{+1}\beta$) and an electron neutrino ($\nu_e$), with an up quark changing to a down quark ($u \rightarrow d + e^+ + \nu_e$).

Fundamental Particle

A subatomic particle that possesses no substructure and is not composed of smaller constituent entities (for example, leptons and quarks).

Quark

An elementary fundamental particle and constituent of hadrons that experiences the strong interaction, with flavors including up ($+\frac{2}{3}e$), down ($-\frac{1}{3}e$), and strange ($-\frac{1}{3}e$).

Lepton

A fundamental particle that does not interact via the strong nuclear interaction, such as electrons, positrons, neutrinos, and antineutrinos.

Hadron

A subatomic particle composed of quarks held together by the strong interaction (including baryons composed of three quarks, like protons and neutrons, and mesons composed of a quark-antiquark pair).

Battery of Cells (Circuit Symbol)

The standard schematic circuit representation consisting of alternating long thin lines (positive terminals) and short thick lines (negative terminals) separated by dashed connections, indicating multiple interconnected electrochemical cells.

Operational Amplifier (Circuit Symbol)

The standard schematic circuit representation featuring a triangle with two input lines (inverting labeled '$-$' and non-inverting labeled '$+$'), positive and negative power rail lines, and a single output line.

Light-Dependent Resistor (LDR Circuit Symbol)

The standard schematic electrical symbol comprising a rectangular fixed-resistor outline with two inward-pointing parallel arrows signifying incident light.