Comprehensive Physics Lecture – Mechanics, Waves, Electricity & Magnetism

Vocabulary flashcards summarising key terms and definitions from mechanics, motion graphs, waves, sound, electromagnetic radiation, magnetism, electrostatics, electric circuits and resistance topics covered in the lecture notes.

Speed

Rate at which distance is covered; scalar quantity measured in m·s⁻¹.

Velocity

Rate of change of displacement; vector quantity with magnitude and direction, measured in m·s⁻¹.

Scalar

Physical quantity described only by magnitude (e.g., distance, speed, mass).

Vector

Physical quantity described by both magnitude and direction (e.g., displacement, velocity, force).

Average Speed

Total distance travelled divided by total time taken.

Average Velocity

Total displacement divided by total time taken.

Instantaneous Speed/Velocity

Speed or velocity at a specific instant; found using the tangent on a position–time graph.

Acceleration

Rate of change of velocity; vector measured in m·s⁻².

Constant Velocity

Motion with unchanging speed and direction; zero acceleration.

Constant Acceleration

Velocity changes by the same amount each second.

Ticker Timer

Laboratory device (50 Hz; dot spacing 0.02 s) used to record motion on a tape.

Frame of Reference

Coordinate system (origin and axes) relative to which position, displacement and motion are described.

Displacement

Straight-line change in position from start to finish; vector measured in metres.

Distance

Actual path length travelled; scalar measured in metres.

Resultant Vector

Single vector that has the same effect as two or more combined vectors; also called net vector.

Equilibrant

Vector equal in magnitude but opposite in direction to the resultant; brings a system into equilibrium.

Vector Diagram (Tail-to-Head)

Graphical method of adding vectors by placing the tail of each at the head of the previous one.

Conversion Factor 3.6

Multiply m·s⁻¹ by 3.6 to obtain km·h⁻¹; divide km·h⁻¹ by 3.6 for m·s⁻¹.

Equation of Motion 1

vf = vi + aΔt (links final velocity, initial velocity, acceleration, time).

Equation of Motion 2

vf² = vi² + 2aΔx (relates velocities, acceleration and displacement).

Thinking (Reaction) Distance

Distance travelled at constant velocity while driver reacts before braking.

Braking Distance

Distance travelled while decelerating (negative acceleration) to a stop.

Stopping Distance

Sum of thinking distance and braking distance.

Gradient of x-t Graph

Slope equals velocity.

Gradient of v-t Graph

Slope equals acceleration.

Area under v-t Graph

Represents displacement.

Pulse

Single, non-repeated disturbance that moves through a medium.

Medium

Substance through which a pulse or wave propagates; particles themselves do not travel with the wave.

Amplitude (Wave)

Maximum displacement of a particle from its rest position.

Pulse Length

Distance from the start to the end of a single pulse.

Pulse Speed

Distance a pulse travels per unit time (v = d⁄t).

Transverse Pulse

Pulse where particle disturbance is perpendicular to direction of propagation.

Longitudinal Pulse

Pulse where particle disturbance is parallel to direction of propagation (compression & rarefaction).

Transverse Wave

Regular sequence of transverse pulses; disturbance perpendicular to motion (e.g., water, EM waves).

Longitudinal Wave

Wave with disturbance parallel to motion (e.g., sound in air, coils in slinky).

Principle of Superposition

When pulses meet, the resultant displacement is the algebraic sum of individual displacements.

Constructive Interference

Two pulses on same side combine to form a larger amplitude.

Destructive Interference

Two pulses on opposite sides combine to reduce amplitude.

Crest

Highest point of a transverse wave above rest position.

Trough

Lowest point of a transverse wave below rest position.

Wavelength (λ)

Distance between two successive points in phase (e.g., crest-to-crest, compression-to-compression).

Frequency (f)

Number of complete waves passing a point per second; measured in hertz (Hz).

Period (T)

Time for one complete wave; T = 1⁄f.

Wave Speed Equation

v = fλ (speed equals frequency times wavelength).

Sound Wave

Longitudinal mechanical wave requiring a medium; propagates as pressure variations.

Speed of Sound in Air

Approximately 340 m·s⁻¹ (varies with temperature, faster in warm air).

Pitch

Perceived highness or lowness of sound; depends on frequency.

Loudness

Perceived volume of sound; related to amplitude and energy.

Quality (Timbre)

Characteristic tone of a sound determined by waveform and harmonics.

Echo

Distinct reflected sound heard after original; requires sufficient surface distance.

Reverberation

Prolongation of sound due to multiple reflections in a confined space.

Ultrasound

Sound waves with frequencies above 20 kHz; used in medical imaging and sonar.

Electromagnetic Radiation (EMR)

Transverse waves of coupled changing electric and magnetic fields; no medium required.

Photon

Quantum (packet) of EM energy; displays particle nature of light.

Wave-Particle Duality

Light and EMR exhibit both wave behaviours (diffraction, interference) and particle properties (photons).

Speed of Light (c)

Constant 3.0 × 10⁸ m·s⁻¹ in vacuum.

Planck’s Constant (h)

6.63 × 10⁻³⁴ J·s; relates photon energy to frequency (E = hf).

Infrared Radiation

EM waves with wavelengths longer than red light; carry heat energy.

Ultraviolet Radiation

EM waves with wavelengths shorter than violet light; can kill microbes, cause fluorescence.

X-Rays

High-energy EM waves that penetrate soft tissue but are absorbed by bone; used in imaging.

Gamma Rays

Highest-energy EM waves; emitted from nuclear processes, used in cancer therapy.

Diffraction

Bending or spreading of waves around obstacles or through openings.

Polarisation

Restriction of wave vibrations to a single plane; property of transverse waves (e.g., light).

Magnetism

Non-contact force due to moving electric charges; produces attraction or repulsion between poles.

Magnetic Pole

Region of a magnet where field is strongest; exists as north and south poles.

Magnetic Field

Region where magnetic forces are experienced; represented by field lines from north to south.

Magnetic Domain

Microscopic region in ferromagnetic material where atomic magnets are aligned.

Ferromagnetic Substance

Material strongly attracted to magnets (e.g., iron, cobalt, nickel).

Temporary Magnet

Material that becomes magnetic easily but loses magnetism quickly.

Permanent Magnet

Material difficult to magnetise but retains magnetism for a long time.

Earth’s Magnetic Field

Global field generated by molten iron movements in Earth’s core; guides compass needles.

Magnetosphere

Region of space dominated by Earth’s magnetic field, shielding the planet from solar wind.

Aurora

Light display near poles caused by charged solar particles exciting atmospheric gases.

Magnetic Declination

Angle between geographic north and magnetic north (≈ 11.5° at present).

Static Electricity

Accumulation of electric charge at rest on an object’s surface.

Law of Conservation of Charge

Total charge in an isolated system remains constant; charges are transferred, not created or destroyed.

Law of Quantisation of Charge

Charge exists in integer multiples of elementary charge (e = 1.6 × 10⁻¹⁹ C).

Coulomb (C)

SI unit of electric charge; 1 C equals charge of ~6.25 × 10¹⁸ electrons.

Polarisation (Electrostatics)

Redistribution of charges in a neutral object due to a nearby charged object, creating a temporary dipole.

Triboelectric Charging

Transfer of electrons between objects through friction (rubbing).

Insulator

Material in which electrons are bound and do not move freely (e.g., plastic, glass).

Conductor

Material with free electrons that allow charge to move easily (e.g., copper).

Electroscope

Instrument with metal leaves used to detect and indicate electric charge.

Electric Current (I)

Rate of flow of charge; measured in amperes (1 A = 1 C·s⁻¹).

Potential Difference (V)

Energy transferred per unit charge between two points; measured in volts.

Electromotive Force (EMF)

Total energy supplied per coulomb by a cell when no current flows.

Terminal Potential Difference

Voltage across a battery when current is flowing; less than EMF due to internal resistance.

Internal Resistance

Resistance inside a cell causing energy loss as heat when current flows.

Series Circuit

Components connected end-to-end; same current flows, voltages add, resistances add (R_T = R₁+R₂…).

Parallel Circuit

Components connected across the same two points; voltages equal, currents split, 1⁄R_T = Σ1⁄R.

Ammeter

Device measuring current; low resistance; connected in series.

Voltmeter

Device measuring potential difference; high resistance; connected in parallel.

Rheostat (Variable Resistor)

Resistor whose resistance can be adjusted to control current.

Resistance (R)

Opposition to charge flow; R = V⁄I; measured in ohms (Ω).

Ohm’s Law

Current through a resistor is directly proportional to potential difference across it at constant temperature.

Factors Affecting Resistance

Increases with longer length, thinner conductor, higher temperature, and higher-resistivity materials.

Resistor

Component that converts electrical energy into heat and limits current in a circuit.

Power Dissipated by Resistor

P = VI = I²R = V²⁄R (rate at which electrical energy is converted into heat).