Explore further together
Start near the axle, remember the test and then move both weights towards the rear.
Your trailer setup, your test
Build a vehicle and trailer setup. Explore together how the vehicle, axles and cargo change its sway.
Nallo’s guide for parents
Ready for the driving test0.0 sDirection of travel →
Drag the crates along their tracks or move the axle group with its yellow handle. Cargo stays secured. During a test, choose “Set up again” before changing anything.
Move the cargo. What will happen after the brief steering input?
Show measurements
Largest sway angle—
Centre of mass relative to axle—
Model hitch load—
Sway after the steering inputAngle between vehicle and trailer
Current testRemembered test
Look closely
Explanation guide for parents and model limits
How you can explain it: “The car gives the trailer a small sideways nudge. Whether the sway settles also depends on where the cargo sits and how fast the setup moves.” Show the movement first; look at the measurements afterwards.
Conversation prompt: “What did we change between these two tests? What stayed the same?” The centre of mass describes the average position of the mass. Rotational inertia describes how much the distributed mass resists a change in rotation.
Vehicle and trailer affect each other through the hitch. Cargo changes total mass, centre of mass, rotational inertia and static wheel loads. Sideways tyre forces depend on slip angle and are limited. With two axles, the model shares the trailer wheel load equally. Each axle acts at its own position; a second set of wheels does not double the total wheel load. Cargo remains secured.
Model limits: Vehicle and tyre values are plausible model assumptions, without calibration to a particular real setup. The model stops at a 25° hitch angle. Pitch, rollover, braking and stability control are not included. Displayed speeds are not driving recommendations. “Far forward” is not a general loading recommendation: the permitted hitch load also matters.
Build your light course
Create a light path with mirrors and obstacles. Can one ray reach the target — and can a whole bundle?
Nallo’s guide for parents
Light off · predict firstTarget not tested yet
Mirror 1
Place parts, drag them by their centres and turn mirrors with the yellow handles. The source, target and obstacles can also move. Keyboard: arrow keys move; Shift + arrow keys rotate. Sliders provide an alternative to dragging.
Predict first: where will the ray go after the mirror?
Show measurements
Reflections—
Angle of incidence at selected mirror—
Angle of reflection at selected mirror—
Explore further together
Turn and move mirrors in the scene. Switch on the light and compare your prediction with its path.
In a guided test, changing the setup switches the light off. In your own workbench, it stays on and responds immediately. Try routing one ray, then a fan of rays, around an obstacle.
Explanation guide for parents and model limits
How you can explain it: “The mirror redirects the light. Imagine a line perpendicular to its surface: the normal. The ray arrives on one side at the same angle that it leaves on the other side.” Both angles are measured relative to the normal.
Conversation prompt: “If I turn the mirror a little, will the light still hit the target?” Rotating a mirror by 5° changes the reflected ray direction by 10°, provided the ray still hits that mirror.
A ray always hits the nearest object first. At the bright front of a flat mirror, angle of incidence equals angle of reflection, both measured from the normal. Mirror backs and obstacles stop the ray.
One or three idealised rays, with at most 24 reflections per ray. Each ray in a bundle is calculated separately. No diffraction, scattering, lenses or mirror images. The drawn path makes the ray visible for explanation.
Build and test your canal lock
Install gates and water passages. Choose your chamber size and test whether the boat can complete the change in height.
Nallo’s guide for parents
1 · Build
Your single-chamber canal lock
Choose a gate or water passage and tap a matching connection in the plan. Yellow handles resize the chamber. Buttons and sliders also let you adjust every part and dimension.
Floor area Water for the lift Filling at 100%
Ready for an upward passageModel time · 0 s
Tap gates and boat in the scene. Drag the yellow valve handles or use the labelled sliders. The yellow button also guides you through the test without dragging.
Move the boat into the chamber. What needs closing next?
Predict what will happen
What lifts the boat?Discuss your prediction before testing.
Show measurements
Chamber water level1.60 m
Water from the upper canal0 m³
Water into the lower canal0 m³
Boat draught—
Current flow rate—
Look closely
What changes in this test?
Watch the water and the boat. Discuss the explanation after observing.
Explore further together
The boat always floats on the water. What lifts it?
Explanation guide for parents and model limits
How you can explain it: “The boat floats on the water. As the chamber water rises, the boat rises too. When the water falls, the boat moves down with it. The gate is simply a door to the other canal.”
Conversation prompt: “If we open the valve only a little, will less water enter in the end, or will it just take longer?” Compare the same lift and change only the opening.
Your plan sets the floor area and height difference. Water needed = chamber length × chamber width × lift height. A 10 × 4 m chamber with a 3 m lift needs 120 m³. A smaller opening takes longer but does not save water when starting and finishing levels are unchanged.
Flow rate is approximately proportional to the square root of the difference in water levels. Large canal sections keep their levels while water is taken from them or flows into them. With unchanged loading, the floating boat displaces a constant volume of water.
Interlocks belong to this learning simulation. Real locks may operate differently. We do not model swirling water or flow forces on the boat. Filling times are model values.
BUILD 21 · 12 LABS · 12 OCT 2026