Fireworks Physics #400
Lab #400 in the Iris collection. A particle physics simulation of fireworks — each mortar shell ascends, then explodes into hundreds of sparks governed by real physics: gravity, air drag, and burst velocity distribution. Five shell types produce distinct patterns. Click the sky to launch. F = mg − ½ρCdAv²
The physics of fireworks
A firework mortar shell is launched upward by a lift charge. As it ascends, gravity decelerates it while air drag further slows the rise. At the apex, a time-fuse ignites the burst charge, ejecting hundreds of stars (pyrotechnic pellets) outward. Each star becomes a projectile subject to the equation F = mg − ½ρCdAv², where the drag force opposes motion and scales with the square of velocity.
Shell types
Peony shells produce a spherical burst — stars radiate uniformly in all directions. Ring (Saturn) shells concentrate stars in a toroidal plane, creating a glowing circle. Willow shells use slow-burning stars with low drag, producing long trailing arcs that droop under gravity. Palm shells fire stars primarily upward with thick trails, creating a palm-tree silhouette. Crossette shells launch a small number of large stars that each split into secondary bursts after a short delay.
Lab #400
This is the 400th interactive lab in the Iris collection — a milestone worth celebrating with a little pyrotechnic display. Every spark on screen obeys Newtonian mechanics, with configurable gravity, drag, and particle count. The rendering uses additive blending for realistic glow, and multi-layer trail persistence for that signature firework shimmer.