Bonisa

Bonisa (“show” in isiZulu) turns a phone video of a physics experiment into a verified scientific measurement. We start with the pendulum, the classic lab for measuring gravitational acceleration g. The problem: In most school and university labs, students time a pendulum with a stopwatch. Human reaction time (about 0.2 s) dominates the error. Results like 9.3 or 10.4 m/s² are common, and nothing tells the student whether the measurement can be trusted. Labs in under-resourced schools, like many in South Africa, can’t afford light gates or motion sensors, but every student has a phone. How Bonisa works: Meta SAM 3.1 (via the Meta Model API) tracks the pendulum bob through every frame from a plain-language prompt such as “orange ball”. It also finds an A4 sheet on the wall, which converts pixels to metres. Physics engine (Python, NumPy/SciPy): Fits a damped oscillation to the motion using each frame’s real timestamp, since phones record at variable frame rates. Fits a circle to the arc to locate the pivot and measure the string length from the video itself. Corrects for swing angle, then computes g = 4π²L/T² with a properly propagated uncertainty. Self-verification: Eight physics checks: tracking coverage time resolution number of swings model fit swing angle camera tilt, detected from the A4 sheet’s aspect ratio video length against the tape-measure length final precision Bonisa reports verified, verified with warnings or rejected. If any check fails, it refuses to give a number and explains in plain language how to fix the setup. An instrument that says “I don’t trust this” is more valuable than one that always answers. Results so far: On a simulated pendulum (true g = 9.81 m/s²), Bonisa measured g = 9.824 ± 0.042 m/s² and recovered the string length from video alone (69.9 cm vs 70 cm). It correctly rejected a too-short recording and a tilted-camera recording. The live SAM 3.1 integration is working end to end on real lab footage. On a real chalkboard video where the bob was a tiny dark object, SAM found nothing, and Bonisa stopped instead of guessing. Next: Muse-powered explanations and re-filming advice in English, isiZulu and isiXhosa. The same pipeline applied to springs, falling objects and projectiles, making Bonisa a general measurement layer for any lab with a phone.