Bouncing Balls Physics (2D)

Physics

Gravity 16.0 m/s²

Restitution (bounciness) 0.80

Ball count 36

Spawn rate Medium

Live Readout

Balls on screen

Kinetic energy

0.0 J

Avg speed

0.0 m/s

Collisions/s

How it works

Each ball free-falls under gravity g and is integrated with semi-implicit Euler in 3 sub-steps per frame for stability at high ball counts. Floor and wall hits flip the normal velocity component and scale it by the restitution coefficient e (0 = perfectly inelastic, 1 = perfectly elastic):

v_n' = -e · v_n   (on contact with a boundary)

Ball–ball collisions use an impulse-based elastic response along the contact normal, weighted by each ball's mass (proportional to its volume, m ∝ r³), plus a mass-weighted position correction so balls don't sink into each other:

j = -(1+e)·(v_rel · n̂) / (1/m1 + 1/m2)
v1' = v1 - j·n̂/m1,  v2' = v2 + j·n̂/m2

This is an O(n²) pairwise check every sub-step — fine for the tens-to-low-hundreds of balls this pit supports. Raise the spawn rate to keep the pit topped up, or hit Burst to drop a fresh handful in from above.

Balls (hue = spawn order) Floor / wall contact