Sandbox
Every simulation, unlocked
The same simulations the lessons use, with every control unlocked and nothing graded. Each one suggests something to try. Change any parameter, then copy the link to share the exact configuration you are looking at.
Classical Mechanics
Read the Classical Mechanics lessons →Motion in One Dimension
Drive a cart and read its position, velocity and acceleration graphs as they are written.
Taught in Motion in One Dimension
Projectile Motion
Launch a body and watch the horizontal and vertical motions run independently, until you switch on air resistance.
Taught in Projectile Motion
Newton's Laws & Free-Body Diagrams
Pull a cart with a force you control and see why steady motion needs no net force at all.
Taught in Newton's Laws & Free-Body Diagrams
Friction on an Incline
Tilt a ramp until the block breaks free, and find the angle where static friction gives up.
Taught in Friction & Inclines
Uniform Circular Motion
Swing a mass on a string, then cut it, and see which way it actually goes.
Taught in Uniform Circular Motion
Work & Energy
Send a skater down a track and watch kinetic and potential energy trade back and forth.
Taught in Work & Energy
Momentum & Collisions
Collide two carts at any restitution and check what survives the impact and what doesn't.
Taught in Momentum & Collisions
The Rolling Race
Race a hoop, a disk and a sphere down the same ramp. Mass and radius won't save the loser.
Taught in Rotation, Torque & Rolling
Angular Momentum
Pull the weights in and watch a spinning platform speed up, in three dimensions.
Taught in Angular Momentum
Gravitation & Orbits
Set a planet loose around a star and discover Kepler's laws by missing them.
Taught in Gravitation & Orbits
Simple Harmonic Motion
Compare a mass on a spring with a pendulum, and find where the pendulum's honesty runs out.
Taught in Simple Harmonic Motion
Damping & Resonance
Drive an oscillator across its natural frequency and watch the amplitude blow up, or not.
Taught in Damping, Driving & Resonance
Waves & Sound
Read the Waves & Sound lessons →Wave Pulses on a String
Flick a pulse down a rope, bounce it off the end, and send a second one to meet it head-on.
Taught in Wave Pulses & Superposition
Standing Waves & Harmonics
Add two identical waves running opposite ways and watch a pattern appear that never travels.
Taught in Standing Waves & Harmonics
Sound as a Pressure Wave
Watch air bunch and spread as a tone passes through it, then add a second tone and hear the loudness swing.
Taught in Sound Waves & Beats
The Doppler Effect
Watch a source outrun its own wavefronts, and read the pitch an observer actually hears.
Taught in The Doppler Effect
Fluids & Thermal Physics
Read the Fluids & Thermal Physics lessons →Pressure & Buoyancy
Release a block in a tank of fluid and find out what actually decides whether it floats.
Taught in Pressure & Buoyancy
Continuity & Bernoulli
Push a liquid through a pipe that narrows, and watch the pressure fall exactly where the fluid speeds up.
Taught in Fluid Flow & Bernoulli's Equation
Heat, Temperature & Thermal Equilibrium
Put two bodies in contact and watch them meet at the heat-capacity-weighted mean, not at the midpoint.
Taught in Heat & Thermal Equilibrium
Kinetic Theory & the Gas Laws
A few hundred molecules in a box. The pressure is measured from the impulse they deliver to the walls, not assumed.
Taught in Kinetic Theory & the Gas Laws
Thermodynamic Processes & Engines
Push a gas around a P–V loop, watch the first law close at every step, and find out why no engine reaches 100 %.
Taught in Thermodynamic Processes & Engines
Electricity & Magnetism
Read the Electricity & Magnetism lessons →Charges & the Electric Field
Map the field of a few point charges, then launch a test charge into it and watch it refuse to follow the lines.
Taught in Charges & Electric Fields
Flux & Gauss's Law
Count the field crossing a surface you choose, and discover the total only cares what is inside it.
Taught in Flux & Gauss's Law
Potential, Equipotentials & Energy
Carry a charge from A to B along four different routes and get the same answer every time.
Taught in Electric Potential & Energy
Current, Resistance & Circuits
Send charge round a loop and count it past every point: current is not used up on the way.
Taught in Current, Resistance & Circuits
Magnetic Fields & the Lorentz Force
Send a charge through a magnetic field and watch a force that turns it without ever speeding it up.
Taught in Magnetic Fields & Forces
Faraday's Law & Lenz's Law
Move a magnet past a coil and watch a current appear. Then hold it still inside and watch the current vanish while the flux stays at its maximum.
Taught in Induction & Faraday's Law
Reflection, Refraction & Total Internal Reflection
Send a wave at a boundary and watch it split: one ray back, one ray on, and one rule deciding both.
Taught in Reflection & Refraction
Lenses, Mirrors & Images
Trace an image into existence with three rays, then find out whether any light is really there.
Taught in Lenses, Mirrors & Images
Two-Slit Interference
Two coherent sources, one extra half-wavelength of path, and light that adds up to darkness.
Taught in Two-Slit Interference
Diffraction, Gratings & Polarization
Narrow a slit and watch the light spread wider; add slits and watch the same lines sharpen; then get light through two crossed polarisers.
Taught in Diffraction & Polarization
Modern Physics
Read the Modern Physics lessons →Time Dilation & Length Contraction
One light clock, two frames, and the geometry that makes both observers right.
Taught in Special Relativity
The Photoelectric Effect
Shine light on a metal, hold the escaping electrons back with a voltage, and read Planck's constant off the slope.
Taught in The Photoelectric Effect
Atomic Spectra & Energy Levels
Drop an electron one rung down a hydrogen atom's ladder and watch the photon it makes land on the spectrum at its own wavelength.
Taught in Atomic Spectra & Energy Levels
A Particle in a Box
Trap a particle between two walls and read off the standing waves it is allowed, the energies that go with them, and the places it is never found.
Taught in Quantum States & the Wavefunction
Radioactive Decay & Half-Life
Watch a few hundred nuclei decay at their own unpredictable moments, and a curve nobody imposed appear anyway.
Taught in Radioactive Decay