Changing speed at fixed persistence time separates linear motion from squared spread. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
One metre per second gives one square metre per second
Hold persistence time at 2 s. Speed 1 m/s gives active spread scale 1 square metre per second.
12⋅2/2=1
Two metres per second gives four
At speed 2 m/s, the squared speed makes active spread 4 square metres per second.
22⋅2/2=4
Three metres per second gives nine
Speed 3 m/s gives active spread 9 square metres per second. The time is still fixed at 2 s.