Conservation of mass · open system
Turn the taps. Whatever the bucket holds changes at exactly the rate mass enters minus the rate it leaves — nothing else.
The bucket is gaining mass: the tap above delivers more than the faucet lets out.
Bucket capacity 100 kg Taps 0 – 10 kg/s Charts last 45 s, hover to read a value Try equal taps → steady state; then full bucket → the spill term appears