THE MAGNETIC INSTRUMENT ROOM
Polekeeper
One layout. Three different beginnings.
Tap numbered sockets to install or remove magnets. The fixed red pole attracts them, turning the free wheel. Your layout must guide all three release angles into their target pointer sectors, within 6° and nearly stopped after 60 simulated seconds.
Angles run counterclockwise from the right. Socket 0 sits on the gold pointer. First job: install one magnet in socket 0, then test all releases. Later jobs need several competing magnetic wells.
Forces, integration & source
Red arrows show the inverse-square attraction on each wheel magnet. Their cross products with radius sum to torque. The wheel follows angular acceleration = torque − damping × angular speed, with unit inertia. Radius 0.70 and fixed-pole distance 0.95 guarantee a 0.25 clearance; no coincident singularity is possible. Fixed-step RK4 uses 0.01 simulated seconds. The animation compresses 60 simulated seconds into four real seconds.
Force and damped-rotation equations adapted from myphysicslab MagnetWheel and MagnetWheelSim; original discrete socket missions and RK4 wrapper. Apache-2.0, 452 stars observed; mature source last updated November 2024. A simplified point-magnet model, not a design tool for real magnets. License · Changes & credits.