Comprehensive Vocabulary Flashcards for Motion, Forces, Energy, and Related Topics (Video Notes)

A set of vocabulary-style flashcards covering key concepts, terms, and formulas from the lecture notes across motion, thermal physics, waves, electricity & magnetism, nuclear physics, and space physics.

Speed

Rate of distance travelled per unit time; a scalar quantity with magnitude only.

Velocity

Speed in a given direction; a vector quantity with magnitude and direction.

Distance

Total length travelled by an object; a scalar quantity with magnitude only.

Displacement

Change in position; a vector quantity from start to finish.

Acceleration

Rate of change of velocity; a vector quantity.

Falling object in vacuum vs with air resistance

In vacuum: constant acceleration (g); with air resistance: velocity approaches a terminal value as drag balances weight.

Terminal Velocity

Constant speed reached by a falling object when drag equals driving force.

Air resistance (drag)

Force opposing motion through air; increases with speed.

Uniform gravitational field

A field where the gravitational acceleration is constant throughout the region.

Weight

Gravitational force acting on a mass; W = m × g.

Mass

Quantity of matter in an object; intrinsic property independent of gravity.

Gravitational field strength (g)

Acceleration due to gravity near Earth’s surface; approximately 9.8 m/s².

Density (ρ)

Mass per unit volume; density = mass/volume.

Volume

Space occupied by a substance; for regular solids measured by dimensions, for irregular solids by displacement.

Pressure (P)

Force per unit area; P = F/A.

Density of water and buoyancy intuition

Objects with density lower than liquid float; higher density sink.

Weight equation

Weight equals mass times gravitational field strength: W = m g.

Centre of gravity

Point where the entire weight of a body can be considered to act; affects stability.

Centre of mass

Point where the mass of an object can be considered to be concentrated; coincides with CG for uniform gravity.

Moment (of a force)

Turning effect of a force; moment = force × perpendicular distance from pivot.

Principle of moments

At equilibrium, total clockwise moments equal total anticlockwise moments.

Equilibrium (no resultant force/moment)

State where there is no net force or moment causing motion or rotation.

Spring constant (k)

Force per unit extension in a spring (Hooke’s law: F = kx).

Limit of proportionality

Point beyond which extension is no longer proportional to the applied force for an elastic object.

Resultant force

Single force that has the same effect as all the forces acting together.

Newton’s second law

F = ma; acceleration is produced when a net force acts on a mass.

Momentum

Mass × velocity; p = mv.

Impulse

Change in momentum; impulse = force × time (FΔt = Δp).

Conservation of momentum

In a closed system with no external forces, total momentum remains constant.

Friction (solid, drag in fluids)

Opposes motion between surfaces (solid friction) or between a body and a fluid (drag).

Centre of gravity determination method

Hang irregular object at two points and use plumb lines to locate CG where lines intersect.

State of matter

Solid, liquid, or gas based on particle arrangement and movement.

Melting

Solid turns into liquid at its melting point.

Freezing

Liquid turns into solid at its freezing point.

Vaporization (evaporation/boiling)

Liquid turns into gas; evaporation occurs at surface, boiling throughout the liquid.

Condensation

Gas turns into liquid as particles lose energy.

Sublimation

Solid changes directly to gas (not explicitly in notes, but related to phase changes).

Specific heat capacity (c)

Energy required to raise the temperature of 1 kg of a substance by 1 K; Q = m c ΔT.

Thermal expansion

Materials expand when heated; expansion is not an increase in particle size but increased spacing.

Absolute zero

Lowest possible temperature (-273°C or 0 K) where particle motion ceases.

Kelvin scale

Temperature scale starting at absolute zero; changes of 1 K equal 1°C change.

Gas law ( Boyle’s law)

At constant temperature, P1V1 = P2V2; pressure and volume are inversely related.

Heat transfer modes

Conduction (through direct contact), convection (mass movement in fluids), radiation (emission/absorption of EM radiation).

Thermal conductors/insulators

Conductors allow energy transfer easily (often metals with free electrons); insulators resist transfer.

Emissivity/absorptivity

Materials that are good emitters/absorbers radiate/absorb heat effectively (e.g., matt black surfaces).

Greenhouse effect

Atmosphere traps heat by absorbing infrared radiation from Earth, warming the surface.

Wave

A disturbance that transfers energy through a medium or vacuum; does not necessarily transfer matter.

Amplitude

Maximum displacement of a point on a wave from its rest position.

Wavelength

Distance between consecutive crests (or troughs) of a wave.

Frequency

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

Wave speed

Speed at which a wave travels; v = fλ.

Transverse wave

Vibration is perpendicular to the direction of wave propagation.

Longitudinal wave

Vibration is parallel to the direction of wave propagation.

Refraction

Change of wave direction and speed when crossing a boundary between media.

Reflection

Change in direction of a wave when it strikes a boundary and returns to the original medium.

Critical angle

Angle of incidence at which refraction angle is 90°; beyond this, total internal reflection occurs.

Total internal reflection

All of the wave is reflected back into the original medium when incidence exceeds the critical angle.

Refractive index (n)

Ratio of wave speeds in different media; n = v1/v2 (or n = sin i / sin r in Snell’s law form).

Optical fibre

Thin transparent fibre that guides light by total internal reflection for communication.

Lenses (converging/diverging)

Converging (convex) focuses parallel rays; diverging (concave) spreads them.

Focal length

Distance from lens to focal point where parallel rays meet (or appear to originate).

Real vs virtual image

Real image forms where rays actually converge; virtual image forms where rays appear to diverge.

Monochromatic light

Light of a single wavelength or colour.

Electromagnetic spectrum

Range of EM waves arranged by wavelength/frequency (radio to gamma).

Wave frequency (Hz)

Number of waves per second.

Sound (longitudinal waves)

Vibrations that propagate through a medium; pitch relates to frequency; volume to amplitude.

Speed of sound in air

Approximately 330–350 m/s at room temperature; faster in solids.

Electrostatics

Study of stationary electric charges and fields.

Electric current

Rate of flow of electric charge; I = Q/t.

Conventional current vs electron flow

Conventional current flows from positive to negative; electron flow is opposite.

Coulomb (charge)

Unit of electric charge; like charges repel, opposite charges attract.

Electric field

Region around a charged object where other charges experience a force.

Potential difference (voltage)

Work done per unit charge to move between two points; measured in volts (V).

Resistance (R)

Opposition to current flow; R = V/I; depends on material, length, and cross-section.

Ohm’s law

Current through a conductor is proportional to the voltage across it (V = IR).

Series circuit

Components in a single path; same current flows through all components; P.d. sums.

Parallel circuit

Components connected across the same two points; same P.d. across each branch; currents sum.

Electrical power

Rate of electrical energy transfer; P = IV.

Energy (electric)

Electrical energy: E = IVt; often measured in kilowatt-hours (kWh).

Fuse

Safety device that melts under excess current to protect circuits.

Live/Neutral/Earth wiring

Live (hot) carries current; Neutral completes circuit; Earth provides safety path.

Electromagnetic induction

Generation of emf by changing magnetic conditions in a circuit.

Fleming’s Right-Hand Rule

Rule to determine direction of induced current when a conductor moves in a magnetic field.

Fleming’s Left-Hand Rule

Rule to determine direction of motion, magnetic field, and force in motors.

Transformer

Device that increases or decreases AC voltage via turns on primary and secondary coils.

Transformer efficiency

Power in output coil equals power in input coil (ideally); Pout = Pin.

Nuclear physics

Study of the nucleus, its structure, radioactive decay, and nuclear reactions.

Nucleus

Small, dense, positively charged center of an atom containing protons and neutrons.

Proton

Positively charged subatomic particle in the nucleus.

Neutron

Electrically neutral subatomic particle in the nucleus.

Electron

Negatively charged subatomic particle orbiting the nucleus.

Isotope

Atoms with the same atomic number but different mass numbers.

Nuclear fission

Splitting of a heavy nucleus into lighter nuclei with energy release.

Nuclear fusion

Joining of light nuclei to form a heavier nucleus with energy release.

Radioactivity

Spontaneous emission of radiation from unstable nuclei.

Alpha decay

Emission of a helium nucleus (2 protons, 2 neutrons); reduces Z by 2 and A by 4.

Beta decay

Neutron converts to proton with emission of an electron; Z increases by 1.

Gamma decay

Nucleus emits gamma radiation (high-energy photons) with no change in Z or A.

Half-life

Time required for half of a radioactive sample to decay.

Background radiation

Low-level ionizing radiation from natural and human sources present in environment.