Physics

153 guides

Mechanics

• Acceleration calculator: from velocity, time or distanceFree acceleration calculator: find acceleration from the change in velocity and the time, or from distance, with the equation used and full working.
• Acceleration formula: a = Δv/t with worked examplesThe acceleration formula a = (v − u)/t, units, deceleration, acceleration from force or distance, centripetal and angular acceleration, with examples.
• Angular velocity formula: ω = v/r = 2πf, units, examplesThe angular velocity formula in every form, ω = θ/t, v/r, 2π/T and 2πf, with units, rpm to rad/s, angular frequency, worked examples and practice.
• Braking distance formula: stopping and thinking distanceThe braking distance formula d = v² ÷ 2a, thinking distance = speed × reaction time, stopping distance, the factors that affect each, and worked examples.
• Buoyancy calculator: buoyant force, float or sinkFind the buoyant force on an object with Archimedes' principle, whether it floats or sinks, how much fluid it displaces and its weight in the fluid.
• Centre of mass: definition, how to find it, examplesWhat the centre of mass is, where it is for regular shapes, how to find it with a plumb line or by calculation, and how it decides when an object topples.
• Centripetal force calculator: F = mv²/r and mω²rFree centripetal force calculator: find the force, speed, radius or mass for circular motion, from v or ω, with the period, frequency and acceleration.
• Centripetal force: formula F = mv²/r, with examplesWhat centripetal force is, the formulas F = mv²/r and F = mω²r, centripetal acceleration, what provides the force, and examples from cars to satellites.
• Distance-time graphs: speed from the gradient, examplesHow to read distance-time graphs: what flat, straight and curved lines mean, finding speed from the gradient, tangents for accelerating objects, examples.
• Force calculator: F = ma, weight and mass with stepsFind force, mass or acceleration from F = ma, and weight from W = mg on Earth, the Moon or Mars, with unit conversions and worked examples.
• Force-extension graphs: spring constant and energy storedReading a force-extension graph: Hooke's law, the limit of proportionality, the spring constant from the gradient, energy stored and the spring practical.
• Free fall calculator: time, speed and height of a fallFree fall calculator: find how long a fall takes, how fast it lands or how far it drops, with g = 9.81 m/s², using our SUVAT solver with full working.
• Gravitational field strength: g, W = mg and g = GM/r²What gravitational field strength is, its value on Earth and other planets, W = mg at GCSE, g = GM/r² at A-level, field lines and worked examples.
• Hooke's law calculator: F = kx, spring constant, energyFind the force, spring constant or extension with F = kx, the elastic energy stored, and the combined spring constant of springs in series or parallel.
• Impulse calculator: J = FΔt and change in momentumFree impulse calculator: find impulse from force and time or from a change in velocity, then the average force or contact time, with every step shown.
• Impulse formula: FΔt = Δp, force-time graphs and examplesThe impulse formula FΔt = Δp = mv − mu: units, rebounds, the area under a force-time graph, crumple zones and airbags, with worked examples and practice.
• Momentum calculator: p = mv, impulse and collisionsFind momentum from p = mv, impulse and average force, and the velocities after elastic and perfectly inelastic collisions, with worked examples.
• Net force calculator: resultant force and F = maFind the net (resultant) force on an object, then its acceleration with F = ma, for forces along a line or at angles, with worked examples.
• Newton's first law of motion: inertia, examples, practiceNewton's first law explained: balanced forces, inertia, the GCSE wording, real-life examples, terminal velocity, A-level equilibrium and worked examples.
• Newton's second law: F = ma with worked examplesNewton's second law of motion, F = ma, explained: resultant force, mass and acceleration, free body diagrams, lifts, inertial mass, examples and practice.
• Newton's third law: equal and opposite forces, examplesNewton's third law explained: equal and opposite forces between two objects, how to spot a third law pair, examples from rockets to walking, and practice.
• Non-contact forces and contact forces: GCSE examplesNon-contact forces act at a distance; contact forces need touching. See examples of each, whether upthrust is a contact force, and GCSE worked examples.
• Pressure calculator: P = F/A and fluid pressure ρghFind pressure from force and area, or pressure at a depth in a fluid with P = ρgh, in Pa, kPa, bar, atm, mmHg or psi, with working and worked examples.
• Principle of moments: moment and torque equations explainedThe principle of moments explained: the moment equation M = Fd, balanced seesaws, forces at an angle, beams on two supports, couples and torque, examples.
• Projectile motion calculator: range, height and timeFree projectile motion calculator and simulator: launch at any speed, angle and height, add air resistance, and read the range, height and flight time.
• Projectile motion: how to solve projectile problemsProjectile motion explained: why horizontal and vertical motion are independent, a step-by-step method, worked launches, and the effect of air resistance.
• Speed equation: speed = distance ÷ time, with examplesThe speed equation, speed = distance ÷ time, and the distance equation s = vt: rearranging, units, km/h to m/s, average speed and distance-time graphs.
• Spring constant equation: k = F/e and Hooke's lawThe spring constant equation k = F/e from Hooke's law, units, finding k from a force-extension graph, the limit of proportionality, examples and practice.
• Strain equation: strain = ΔL ÷ L, stress and Young modulusThe strain equation, strain = extension ÷ original length: tensile stress, the Young modulus, stress-strain graphs, strain energy and worked examples.
• Stress strain graph: the key points, gradient and areaStress-strain graphs for A-level Physics: the limit of proportionality, elastic limit, plastic region, breaking stress, Young modulus and area.
• SUVAT calculator: enter any 3 values, get the other 2Enter any three of s, u, v, a and t to find the other two, see which SUVAT equation was used and why, and get both answers when there are two.
• SUVAT equations (kinematic equations): all 5 with examplesAll 5 SUVAT equations, also called the kinematic equations, with a free calculator, worked examples, practice questions and what each exam gives you.
• Torque calculator: τ = Fd, angles and balanceFind torque (moment) from force and distance, including forces at an angle, balance a seesaw with the principle of moments, and find the net torque.
• Upthrust: what it is, why it happens and floatingWhat upthrust is, why fluid pressure causes it, how to measure and calculate it, and why objects float or sink, with worked GCSE Physics examples.
• Velocity calculator: speed, final velocity and v = u + atFind velocity from distance and time, or final velocity from v = u + at and v² = u² + 2as, with a working calculator and worked examples.
• Weight equation: W = mg explained, with examplesThe weight equation W = mg: weight, mass and gravitational field strength, units, rearranging, weight versus mass, newtonmeters and worked examples.
• What is friction? Types, formula and examplesWhat friction is and what causes it, static vs kinetic friction, the formula F = μN with worked examples, air resistance, and how to reduce friction.
• What is momentum? Formula, conservation and examplesWhat momentum is, the momentum formula p = mv, why it is a vector, conservation of momentum in collisions and explosions, and change in momentum.

Energy

• Efficiency calculator: useful output ÷ total inputWork out efficiency as a percentage from useful and total energy or power, or find the useful output or total input, with the wasted energy shown.
• Elastic potential energy formula: Ee = ½ke² explainedThe elastic potential energy formula Ee = ½ke², its units, rearranging for k and extension, the force-extension graph, worked examples and practice.
• Energy stores and transfers: the 8 stores with examplesThe 8 energy stores and 4 ways energy is transferred, with GCSE examples, the equation for each store, worked calculations and practice questions.
• Gravitational potential energy: GPE equation Ep = mghThe gravitational potential energy equation Ep = mgh, units, rearranging, GPE to kinetic energy, lifting and power, worked examples and practice questions.
• Kinetic energy calculator: KE = 1/2 mv² with stepsFind kinetic energy, mass or speed from KE = ½mv², or the change in kinetic energy, with unit conversions and worked examples you can check.
• Kinetic energy equation: Ek = ½mv² explained, with examplesThe kinetic energy equation Ek = ½mv²: what each letter means, how to rearrange it for mass and speed, where it comes from, worked examples and practice.
• Potential energy calculator: mgh and ½kx² with stepsFree potential energy calculator: gravitational energy from mgh and elastic energy from ½kx², or rearrange for mass, height, gravity or extension.

Electricity and magnetism

• Breadboard simulator: test a circuit before you build itTest a breadboard circuit online before you build it: place LEDs, resistors, switches and sensors, read live voltage and current, and spot mistakes first.
• Charge equation Q = It: charge, current and timeThe charge equation Q = It, what charge and current are, units, rearranging, charge and energy with E = QV, electrons per coulomb, examples and practice.
• Coulomb's law calculator: force between two chargesFind the force between two charges with Coulomb's law, F = kQ₁Q₂/r², in C, µC, nC or electron charges, plus field strength, with worked steps.
• Energy transferred equation: E = Pt and E = QV, examplesThe energy transferred equations E = Pt and E = QV explained: units, rearranging, kilowatt-hours, work done and efficiency, with examples and practice.
• Fleming's left hand rule: how to use it, with examplesHow Fleming's left hand rule gives the direction of the force on a current in a magnetic field, the motor effect, F = BIl, worked examples and practice.
• How to calculate voltage drop: formula and examplesHow to calculate voltage drop with V = IR: across resistors in series, in a potential divider, inside a battery and along a cable, with worked examples.
• I-V characteristics required practical: method and resultsThe I-V characteristics required practical for a filament lamp, a resistor and a diode: circuit, method, variables, results, analysis, risks and errors.
• I-V characteristics: resistor, filament lamp and diodeI-V characteristic graphs for a resistor, a filament lamp and a diode: what each shape means, how to find resistance from them, and the circuit you use.
• Internal resistance: emf, terminal pd and lost voltsInternal resistance for A-level Physics: emf, terminal pd and lost volts, ε = I(R + r), the required practical and its graph, with worked examples.
• Kirchhoff's second law: the loop rule, with examplesKirchhoff's second law explained: the sum of the emfs round any closed loop equals the sum of the potential differences, with loop examples and practice.
• Light dependent resistor (LDR): how it works and usesWhat a light dependent resistor is, how its resistance changes with light, its graph and symbol, uses, and how an LDR works in a potential divider circuit.
• Mains electricity: 230 V ac, the three wires and safetyMains electricity for GCSE Physics: ac at 50 Hz and 230 V, live, neutral and earth wires, fuses, power and energy equations, and the National Grid.
• Online circuit simulator: build DC circuits, read metersBuild DC circuits online with cells, resistors, lamps, LEDs, switches, sensors and meters, and see every voltage and current live, with worked examples.
• Parallel resistor calculator: total resistance and currentFind the total resistance of resistors in parallel, the current in each branch and the supply current, with the formula and examples to check.
• Series and parallel circuits: rules, resistors, examplesSeries and parallel circuits explained: current, potential difference and resistance rules, resistors in parallel, and worked GCSE and A-level examples.
• Solenoids: magnetic field, electromagnets and usesWhat a solenoid is, the shape of its magnetic field, how to find its poles, how to make it stronger, electromagnets, and the formula B = μ₀nI.
• Split ring commutator: how it works in a DC motorWhat a split ring commutator is, how it reverses the current every half turn to keep a DC motor spinning, its job in a dynamo, and slip rings compared.
• Thermistor graph: resistance against temperatureHow to read a thermistor graph of resistance against temperature, the I-V graph of a thermistor, using one as a temperature sensor, and worked examples.
• Variable resistors: how they work, symbol and usesWhat a variable resistor does, how potentiometers and rheostats work, their circuit symbol and uses, with GCSE examples and the I-V practical.
• Voltage divider calculator: Vout, loading and sensorsFree voltage divider calculator: find the output voltage from two resistors, see what a load does to it, and try thermistor and LDR sensor circuits.
• What is a capacitor? What it does and how to test oneWhat a capacitor is and what it does, Q = CV and stored energy, charging curves and the time constant, where capacitors are used, and how to test one.
• What is a resistor? What resistors do, with examplesWhat a resistor is and what it does: resistance and Ohm's law, the colour code, choosing an LED resistor, power ratings and types, with examples.
• What is a transistor? What it does and how it worksWhat a transistor is and does: how it works as a switch and an amplifier, NPN and MOSFET types, a worked switch circuit and why chips use billions.
• What is potential difference? Definition, formula, examplesPotential difference is the energy transferred per unit charge between two points. The GCSE and A-level definitions, E = QV, pd vs emf, with examples.
• What is voltage? Meaning, units and examples explainedVoltage is the push that drives electric current: the energy each coulomb of charge carries. Learn what a volt is, how voltage works, with examples.

Waves and light

• Critical angle formula: sin θc = n₂/n₁, with examplesThe critical angle formula sin θc = n₂ ÷ n₁ (or 1 ÷ n into air): how it is derived, total internal reflection, optical fibres, typical values and examples.
• Diffraction grating: d sin θ = nλ explained, with examplesWhat a diffraction grating is, the equation d sin θ = nλ, lines per mm, the maximum order, white light spectra, the required practical and worked examples.
• Is light a wave or a particle? Wave-particle dualityIs light a wave or a particle? The evidence for each, from the double-slit experiment to the photoelectric effect, photon energy E = hf and duality.
• Optics simulator: lenses, mirrors and prisms ray by rayTrace light rays through lenses, mirrors, prisms and glass blocks online, with the image distance, magnification, refraction angles and the critical angle.
• Pendulum simulation: period, energy and damping, liveSwing a virtual pendulum or a mass on a spring, change the length, angle, gravity and damping, and watch the period, the graphs and the energy change.
• Phase and path difference: formulas and examplesPhase difference and path difference explained: measuring them in degrees, radians and wavelengths, how they link, and the conditions for interference.
• Piezoelectric effect: how it works, materials and usesWhat the piezoelectric effect is, why some crystals make a voltage when squeezed, the converse effect, and its uses in ultrasound probes and quartz clocks.
• Polarisation of light: what it is, Polaroid and usesPolarisation for A-level Physics: polarised and unpolarised waves, why only transverse waves polarise, Polaroid filters, crossed polarisers and their uses.
• Radio waves: what they are, uses and how they workRadio waves for GCSE Physics: their place in the electromagnetic spectrum, how aerials make and receive them, their uses, and wavelength calculations.
• Refraction ray diagrams: how to draw and explain themHow to draw a refraction ray diagram, which way light bends at a boundary, the glass block practical, and why refraction happens, using wave fronts.
• Simple harmonic motion: equations, graphs and examplesWhat simple harmonic motion is, a = −ω²x, displacement, velocity and acceleration equations and graphs, springs and pendulums, energy and damping.
• Snell's law calculator: refraction angles and critical angleFree Snell's law calculator: find the angle of refraction, the angle of incidence, a refractive index or the critical angle, with the working shown.
• Snell's law: n₁ sin θ₁ = n₂ sin θ₂ explained, with examplesSnell's law n₁ sin θ₁ = n₂ sin θ₂ explained: refractive index, n = sin i ÷ sin r, bending towards or away from the normal, worked examples and practice.
• Total internal reflection: critical angle and examplesTotal internal reflection explained: the two conditions, the critical angle formula sin C = 1/n with worked examples, optical fibres and everyday uses.
• Wave simulator: ripple tank, interference and slitsFree wave simulator: a ripple tank with two sources, a double slit or a single slit, showing interference, diffraction, path difference and fringe spacing.
• Wave speed equation: v = fλ with worked examplesThe wave speed equation v = fλ, the frequency equation f = 1/T, units and rearranging, worked examples for sound, water and light waves, and practice.
• Wavelength calculator: wavelength, frequency and speedFree wavelength calculator: get wavelength from frequency and wave speed, or frequency from wavelength, for sound or light, with the spectrum region named.
• What is a standing wave? Nodes, antinodes and harmonicsWhat a standing wave is, how it forms, nodes and antinodes, harmonics on strings and in pipes, and worked examples from guitars to microwave ovens.
• What is a transverse wave? Transverse vs longitudinal wavesWhat transverse and longitudinal waves are, how they differ, examples of each, what a mechanical wave is, and worked examples with the wave equation.
• What is a wave? Types, amplitude, frequency and wavelengthA wave carries energy from place to place without carrying matter. Learn the types of wave, amplitude, frequency, wavelength, v = fλ and how to draw one.
• What is an electromagnetic wave? Spectrum, uses, examplesWhat an electromagnetic wave is, how it travels, the electromagnetic spectrum from radio to gamma rays, uses and dangers, and worked examples.
• What type of wave is a sound wave? Sound waves explainedWhat type of wave a sound wave is, how compressions and rarefactions carry it, its speed in air, water and steel, pitch, loudness and worked examples.

Thermal physics and matter

• Boyle's law calculator: P1V1 = P2V2 with stepsFind the new pressure or volume of a gas at constant temperature with Boyle's law, P1V1 = P2V2, in any units, with working, a graph and worked examples.
• Combined gas law calculator: P1V1/T1 = P2V2/T2Solve the combined gas law P1V1/T1 = P2V2/T2 for pressure, volume or temperature, with Celsius converted to kelvin for you and worked examples.
• Density calculator: density, mass or volume, with workingFree density calculator: find density from mass and volume, or mass or volume from density, in kg/m³ or g/cm³, and see whether it floats in water.
• First law of thermodynamics: Q = ΔU + W explainedThe first law of thermodynamics, Q = ΔU + W: sign conventions, work done by a gas W = pΔV, isothermal, adiabatic and constant volume changes, pV diagrams.
• Ideal gas law calculator: PV = nRT for P, V, n or TFree ideal gas law calculator: solve PV = nRT for pressure, volume, moles or temperature, in the units you have, with the working and the molecule count.
• Internal energy: definition, examples and how it changesWhat internal energy is, how heating and doing work change it, why temperature stays constant during a change of state, and the first law at A-level.
• Specific heat calculator: Q = mcΔT and latent heatSolve Q = mcΔT for energy, mass, specific heat capacity or temperature change, plus latent heat and mixing temperatures, with worked examples.
• Specific heat capacity practical: method, results, analysisThe specific heat capacity required practical: equipment, method, results table, finding c from the gradient, risks, errors and improvements, exam tips.
• Specific heat capacity: equation, units and examplesWhat specific heat capacity is, the equation ΔE = mcΔθ, units, the value for water, 6 worked examples, practice questions and what the exam sheets give.
• Specific latent heat: equation E = mL and examplesWhat specific latent heat is, the equation E = mL, latent heat of fusion and vaporisation, heating curves, worked examples and practice questions.

Fields and gravity

• Coulomb's law: F = kQ₁Q₂/r² explained, with examplesCoulomb's law F = Q₁Q₂ ÷ 4πε₀r² explained: the constants, attraction and repulsion, the inverse square law, worked examples and a comparison with gravity.
• Electric potential: V = kQ/r, equipotentials and examplesElectric potential for A-level Physics: what it means, V = Q/4πε₀r for a point charge, potential difference and work done, equipotentials and examples.
• Escape velocity: formula, derivation and examplesThe escape velocity formula v = √(2GM/r), how to derive it, Earth's 11.2 km/s worked out, values for the planets, black holes and practice questions.
• Gravitational force calculator: F = Gm₁m₂/r² with stepsFree gravitational force calculator: the pull between any two masses by Newton's law of gravitation, with the working, unit choices and a force graph.
• Gravitational potential calculator: V = −GM/r and UFree gravitational potential calculator: find V = −GM/r at any distance from a planet, and the potential energy U = −GMm/r of a mass placed there.
• Gravitational potential: V = −GM/r explained with examplesGravitational potential explained: the formula V = −GM/r, why it is negative, potential energy, equipotentials and the link to g, with worked examples.
• Gravity simulator: orbits, escape speed and planetsFree gravity simulator: launch up to six planets round a star, see bound orbits and escapes, and read each period, eccentricity and escape speed live.
• Kepler's third law: formula, derivation and examplesKepler's third law links orbital period and radius. Get the formula, the A-level derivation, four worked examples and a free calculator.
• Lenz's law: why induced currents oppose the changeLenz's law explained: induced currents oppose the change that caused them, why energy conservation demands it, magnets and coils, moving rods and examples.
• Magnetic field simulation: bar magnets and field linesFree magnetic and electric field simulation: drag bar magnets and charges, watch field lines trace live, and probe the field strength anywhere.
• Magnetic flux density: B = F/Il, the tesla and fluxMagnetic flux density explained: B = F ÷ Il, the tesla, F = BQv, magnetic flux Φ = BA, flux linkage and induced emf, with worked examples and practice.

Atoms and particles

• Alpha, beta and gamma decay: equations and propertiesAlpha, beta and gamma radiation compared, with decay equations for alpha, beta minus, beta plus and electron capture, Feynman diagrams and worked examples.
• Binding energy calculator: from the mass defect, in MeVTurn a nucleus's mass defect into its binding energy in MeV or joules, with the working, plus how to find the mass defect and binding energy per nucleon.
• De Broglie wavelength: λ = h/mv with worked examplesThe de Broglie wavelength λ = h/mv explained: what it means, how to use it for electrons and other particles, electron diffraction, and worked examples.
• Feynman diagrams: rules and A-level examplesHow to draw a Feynman diagram: the rules, exchange particles, and diagrams for repulsion, beta minus, beta plus, electron capture and collisions.
• Half-life calculator: amount left, half-life and timeFree half-life calculator: find the amount left after any time, the half-life from your data, or the time to decay, with every step and a decay curve.
• Half-life: definition, graphs and calculationsWhat half-life means, how to find it from a decay graph, GCSE half-life calculations and net decline, and the A-level decay constant, with worked examples.
• Mass defect and binding energy: formula and examplesWhat mass defect and binding energy are, how to calculate them in MeV and joules, binding energy per nucleon, and worked A-level examples.
• Mass number and atomic number: meaning and examplesMass number and atomic number explained: what each tells you, how to read nuclear notation, how to find protons, neutrons and electrons, and isotopes.
• Mass of electron: 9.109 × 10⁻³¹ kg, in kg, u and MeVThe mass of an electron is 9.109 × 10⁻³¹ kg, about 1/1836 of a proton. See it in kg, u and MeV, compared with protons and neutrons, with worked examples.
• Nuclear model of the atom: the alpha scattering experimentWhat the nuclear model of the atom is, how the alpha particle scattering experiment replaced the plum pudding model, and how the model changed after.
• Radioactive decay: activity, half-life and N = N₀e^(−λt)What radioactive decay is, why it is random, activity and count rate, background radiation, half-life, and the decay constant equations for A-level.
• Specific charge: formula, units and worked examplesSpecific charge is charge divided by mass, in C/kg. See the formula, the values for the electron and proton, and worked examples for nuclei and ions.
• Strong nuclear force: range, strength and exchange particlesWhat the strong nuclear force is, why it holds the nucleus together, its range of about 3 fm, the force-separation graph, and pions and gluons.
• Transmission electron microscope: how a TEM worksHow a transmission electron microscope works, why electrons give better resolution, how specimens are prepared, and how a TEM compares with SEM and light.
• Work function: the photoelectric effect explainedWork function, threshold frequency and stopping potential for A-level Physics: the photoelectric equation hf = ϕ + Ek(max), graphs and worked examples.

Space

• Artemis II: How we successfully went to the moonInside the nine-day Artemis II mission: the free-return trajectory, the engineering behind SLS and Orion, the toilet that almost stole the show, and what it means for Artemis III.
• Black hole simulator: light bending and time dilationFree black hole simulator: trace real light paths past a black hole, see the horizon, photon sphere and shadow to scale, and watch a near clock slow.
• Escape velocity calculator: v = √(2GM/r) with stepsFind the escape velocity from any planet, moon or star from its mass and radius, in m/s, km/s, mph or as a fraction of light speed, with worked steps.
• How many galaxies are in the universe? Size, stars, atomsHow many galaxies, stars, planets and atoms are in the universe, how big the observable universe is, and how scientists work it out.
• How old is the universe? 13.8 billion years, explainedThe universe is about 13.8 billion years old. See the three ways scientists measure its age, the Hubble tension, and worked examples you can follow.
• Is the universe infinite? What the universe is made ofIs the universe infinite? What the universe is, how big the observable part is, what it is made of, where its centre is and whether we are alone.
• Life cycle of a star: every stage explained (GCSE)Life cycle of a star from nebula to main sequence, then red giant and white dwarf, or supernova, neutron star and black hole, and how stars make elements
• Orbital period calculator: T from orbit radius and massFind how long an orbit takes from its radius and the central mass, or the orbit radius from the period, with Kepler's third law and worked examples.
• What is the biggest black hole? Black holes explainedWhat a black hole is, what is inside one, what they look like, the biggest and closest known black holes, and whether one could ever hit Earth.
• What is the biggest thing in the universe? And the smallestThe biggest things in the universe, from Jupiter to giant stars, superclusters and the Quipu superstructure, plus the smallest and hottest things known.
• What was before the Big Bang? What we know and don'tWhat the Big Bang was, the evidence for it, how we know the universe is 13.8 billion years old, and the leading ideas about what came before it.

Practical skills

• Percentage uncertainty: formula and how to calculate itThe percentage uncertainty formula, absolute uncertainty from scales and repeats, and how to combine uncertainties when adding, multiplying and squaring.
• Physics prefixes: list, powers of ten and conversionsEvery prefix you need for GCSE and A-level Physics, from tera to femto, with powers of ten, how to convert units, and worked examples from real physics.
• Worst fit line calculator: gradient uncertainty, error barsFree worst fit line calculator: average repeat readings, draw error bars, and find the gradient and intercept with their uncertainties for a write-up.

Courses

• Black holes course: event horizons, lensing and timeAn interactive black holes course in 25 short sections: escape speed, dying stars, the event horizon, lensing, slow clocks and Hawking radiation.
• Blockchain course: how cryptocurrencies really workAn interactive blockchain course in 25 short sections: ledgers, hashes, mining, keys and signatures, proof of stake, smart contracts and scams.
• Cosmology course: the Big Bang, redshift and dark energyAn interactive cosmology course in 24 short sections: expansion, redshift, Hubble's law, the age of the universe, inflation, the CMB and dark energy.
• Electricity physics course: charge, current, voltage, powerAn interactive electricity course in 24 short sections: charge, current, potential difference, Ohm's law, power, AC and DC, plugs and fuses.
• How will the universe end? Big Freeze, Rip or CrunchHow will the universe end? A 22-section course on dark energy, the Big Freeze, Big Rip and Big Crunch, entropy, the last stars and what DESI found.
• Light physics course: waves, photons, reflection, refractionAn interactive light course in 23 short sections: waves, c = fλ, the electromagnetic spectrum, photons, reflection, refraction and Snell's law.
• Nuclear physics course: fission, fusion, decay and half-lifeAn interactive nuclear physics course in 23 short sections: mass defect, binding energy, fission, chain reactions, reactors, decay, half-life and fusion.
• Particle physics course: quarks to the Standard ModelAn interactive particle physics course in 23 short sections: quarks, leptons, force carriers, the Standard Model, antimatter, hadrons and the Higgs.
• Physics mechanics course: Newton's laws, momentum, SUVATAn interactive mechanics course in 25 short sections: velocity-time graphs, forces, Newton's three laws, F = ma, momentum, impulse, SUVAT and projectiles.
• Quantum computing course: qubits, gates and algorithmsAn interactive quantum computing course in 25 short sections: qubits, measurement, the Bloch sphere, gates, entanglement, interference, Grover and Shor.
• What is the smallest thing in the universe? A courseWhat is the smallest thing in the universe? A 23-section course from cells to atoms, nuclei, quarks and the Planck length, measured in powers of ten.