Welcome to NEWTON LAB — build real 3D physics experiments, then check them against the formulas.

Newton Lab — Documentation

Everything you need to run this in a classroom. No install, no login, no internet.

1. The four screens

Screen	What it is for
Experiments	The library. Twenty ready-made benches, grouped by topic. Click a card to open it.
Laboratory	The 3D bench itself: object toolbar on the left, the world in the middle, and the Setup / Properties / Theory / Questions dock on the right.
Diagrams	Plot any recorded quantity against time. Tick several curves to compare them, and leave the dashed theoretical curve on to see how well the model fits.
Documentation	This page.

2. Driving the 3D view

Every camera move can be done with the mouse or from the keyboard — use whichever suits the room.

Action	Mouse	Keyboard
Orbit	Left-drag on empty space	← → ↑ ↓
Pan	Right-drag (or middle-drag)	Shift + arrow keys
Zoom	Mouse wheel	+ and −
Reset the camera	Reset view button	0
Move faster	—	hold Alt with any of the above
Standard views	Front / 3D / Side / Top buttons, top-left of the viewport
Select a body	Left-click it with the Select tool
Drag a body	Left-click and drag it. Paused → it teleports. Running → you pull it with a spring.
Focus on selection	F

Left-drag only orbits when it starts on empty space — starting on a body moves the body, so the two never fight each other.

3. Building your own experiment

1. Open the Empty Bench experiment (bottom of the library).
2. Pick a body from the toolbar — brick, ball, wheel, plank, slope or fixed block — and click in the scene to drop it in.
3. Pick a constraint — pin, rod, rope, spring or motorised hinge — then click body A, then body B. Click empty space as the second click to anchor to the world instead.
4. Select any body and edit its mass, material, friction, elasticity, size, velocity, applied force or torque in Properties.
5. Press Run. Save the whole bench to a .newton file from the menu.

4. Materials

Choosing a material sets density (and therefore mass), friction and restitution together — the same trade-offs a real technician makes when choosing what to build a rig out of.

Material	Density kg/m³	Friction μ	Restitution e
Wood	650	0.40	0.30
Steel	7850	0.30	0.45
Rubber	1200	0.95	0.85
Plastic	1050	0.35	0.55
Ice	917	0.04	0.10
Lead	11340	0.45	0.10
Concrete	2400	0.65	0.15

5. Reading the Theory panel

Each row shows a measured quantity from the running 3D world, the value the textbook formula predicts, and the difference. Green (<2 %) means the model and the world agree. Amber and red mean something in the model is missing — friction, air resistance, rotational inertia, or an approximation such as sinθ ≈ θ. That disagreement is the lesson, not a bug: ask students which assumption has just broken.

6. Free-body diagrams

Select any body and Newton Lab draws its free-body diagram — every force acting on it, drawn separately and to scale, with the numbers listed in the Properties panel.

Arrow	Force	Where it comes from
red	Weight, mg	Gravity. Always present, always straight down.
blue	Normal, N	The surface pushing back, at right angles to it.
orange	Friction, f	Along the surface, opposing sliding.
purple	Tension, T	A rope, rod, spring or pulley pulling.
cyan	Air drag, D	Only when Air resistance is switched on.
black	Resultant, ΣF = ma	The sum of all the others. This is the only one that accelerates the body.

The one thing to take away: weight is not the resultant force. Select a block resting on the ground — the red weight arrow and the blue normal arrow are the same length and point opposite ways, and the black resultant vanishes. No resultant force, no acceleration. That is Newton's first law, and it is the single most common thing to get wrong in an exam.

These forces are not decorative. They are read straight out of the solver — the contact impulses and the joint impulses it actually applied — so the arrows on screen add up to ma exactly.

7. Keyboard

Space run / pause   R reset the experiment   1 select tool   X delete tool   F focus on selection   Del delete selected body

←→↑↓ orbit   Shift+arrows pan   + / − zoom   0 reset the camera   Alt move faster

7. How the physics works

Bodies are rigid, motion is solved in the vertical x–y plane and drawn as extruded 3D solids. Each frame the engine integrates forces, finds contacts (circle–circle, circle–polygon and polygon–polygon with SAT clipping), then runs twelve iterations of a sequential-impulse solver with warm starting for contacts, joints and friction. The time step is fixed at 1/240 s, so results are repeatable.

Gravity, air density, per-body material, applied force and applied torque are all yours to change. Air drag uses F = ½ρCdAv² against the body's frontal area.

8. Classroom ideas

• Predict–observe–explain. Give students the parameters, have them compute the answer first, then run the bench and check the Theory panel.
• Break the model. Push the pendulum past 40°, or turn on air resistance during free fall, and ask which assumption failed.
• Data analysis. Export CSV from the Diagrams tab and graph it in a spreadsheet; gradient of v–t is the acceleration.
• Design task. Give a target — "lift 10 kg with a 3 kg effort" — and let students build the machine on the Empty Bench.