Fig. 1.1Live
Classical mechanics/28 simulations
Double pendulum
Two rods, one hinge, endless outcomes. Watch deterministic chaos unfold from a nudge smaller than a millimetre.
Early access140+ simulations, all running livePhysics you
Physics you
can touch.
Inertia turns the laws of nature into real-time simulations you can push, pull and pick apart. Change a variable and watch the equations change with it.
- Free for students
- Runs in any browser
- Mapped to AP, IB and A-level
Live simulationFig. 0
- Bodies
- 38
- Kinetic energy
- 0.00 J
- Impacts / s
- 0
Drag across the spheres or tap to add energy.Move to disturb the cluster, click to add energy.
- Classical mechanics
- Gravitation
- Waves and optics
- Electromagnetism
- Thermodynamics
- Quantum mechanics
- Special relativity
- Fluid dynamics
- Nuclear physics
- Astrophysics
01Simulations
Every law of nature, running live.
Not videos. Not diagrams. Each simulation is solved frame by frame as you watch, so what you see is exactly what the equations predict.
Every figure in this section is computing physics right now, in your browser. Nothing here is pre-rendered.
Fig. 1.2Live
- Star
- Planet
Gravitation/19 simulations
Kepler orbits
A planet sweeps equal areas in equal times. The shaded wedge stays the same size whether it is racing or crawling.
Fig. 1.3Live
Waves and optics/24 simulations
Two-source interference
Crests meet crests, troughs cancel crests. As the sources drift apart, the fringes fan out and rearrange.
Fig. 1.4Live
- +q
- −q
Electromagnetism/21 simulations
Electric dipole
Field lines leave the positive charge and land on the negative one. Move them closer and every line bends to follow.
Fig. 1.5Live
- Slow
- Typical
- Fast
Thermodynamics/17 simulations
Ideal gas
Seventy particles start at the same speed. Within seconds their speeds spread into the Maxwell-Boltzmann curve.
Fig. 1.6Live
- + phase
- − phase
Quantum mechanics/31 simulations
Hydrogen 3d orbital
Two thousand samples of a real wavefunction, colored by phase. The shape of an electron, finally visible.
02The lab
Momentum, conserved.
Grab a sphere, pull it back and let go. Then take the whole experiment to the Moon or Jupiter and watch the swing stretch out or snap tight.
Fig. 2.1 / Newton's cradle
Ready
Drag a sphere sideways, then let go
03How it works
From intuition to equation in three moves.
Inertia is built around one loop: see something happen, change why it happens, then read the math that explains it.
- Step 0101
- Projectile motionMechanics
- Kepler orbitsOpen
- Standing wavesWaves
- Quantum tunnellingQuantum
Pick a phenomenon
Browse more than 140 simulations organised by topic and syllabus, from projectile motion to quantum tunnelling.
- Step 0202Mass2.0 kgGravityadjustingTime× 0.5
Pull the levers
Every constant is a slider and every object is draggable. Change mass, charge, gravity or the flow of time itself.
- Step 0303
F = m·a
m = 2.0 kga = 4.9 m/s²F = 9.8 NRead the math
Graphs, vectors and equations update live and share colors with the objects they describe, so every symbol has a body.
04Platform
Built like a lab instrument.
Under the friendly surface sits a physics engine that would pass a peer review, wrapped in tools that make teaching and learning faster.
Lab-grade engine
Symplectic integrators and a fixed 240 Hz timestep keep energy honest, even when you fast-forward through a thousand orbits.
Equations that move
Every symbol shares a color with the object it describes, so the formula and the motion read as one thing.
Ek = ½ m v²
v = 3.2 m/s
Any screen, zero installs
Runs smoothly on phones, tablets and school Chromebooks. Nothing to download and nothing for IT to approve.
1 needs help with vectors
- Maya R.92%
- Leo T.64%
- Ines K.81%
Built for classrooms
Assign a simulation, set the starting conditions and see exactly where understanding breaks down.
Tab←→
Accessible by default
Keyboard control for every slider, screen reader descriptions for every scene and captions on every guided tour.
- live simulations
- 140+
- topics, school to university
- 18
- fixed physics timestep
- 240 Hz
- installs or plugins
- 0
05Voices
Loved in classrooms and lecture halls.
What teachers, students and lecturers from our early-access group say after a term with live simulations.
My students used to memorise the pendulum formula. Now they argue about why the period ignores mass, and that argument is the whole point of physics.
Interference finally clicked when I dragged the second source and watched the fringes bend. Two years of textbook diagrams never did that.
The integrators are genuinely correct. I run the orbit simulations live in my mechanics lectures without having to apologise for them.
06Pricing
Free for curious minds. Fair for everyone else.
Student
Everything you need to learn physics on your own terms.
$0Free forever
Start free- All 140+ live simulations
- Live equations, graphs and vectors
- Save up to 10 experiments
- Works on phones, tablets and laptops
Pro
For serious learners, exam prep and independent tutors.
$6per month, billed yearly
Get Pro early- Everything in Student
- Unlimited saved experiments
- Export graphs and data as CSV
- Guided step-by-step derivations
- First access to new simulations
Schools
For classrooms, departments and whole districts.
CustomTailored to your school
Talk to us- Teacher dashboard and assignments
- Google Classroom and LMS sync
- Class-wide understanding analytics
- Single sign-on and admin controls
- Onboarding for your department
07FAQ
Questions, answered.
Everything you might want to know before your first experiment.
No. Inertia runs entirely in your browser on phones, tablets, laptops and school Chromebooks. If a device can open a website, it can run the lab.
08Early access
Put the universe in motion.
Join the early-access list. Students get in free, forever, and schools get a guided pilot with their own classes.