Bad physics in Particle System Fountain

The treatment of gravity and forces is very bad. Yes, the info tab says "Gravity is unrealistic in this system, in that its acceleration changes depending on the particle’s mass. This is an important characteristic of particles systems: We can create motions that do not strictly follow real-world physical rules."

Why present a model in which the acceleration due gravity is proportional to the mass? If one wants students to explore alternative physics then at least add a slider or switch that controls these non-Newtonian features. True that with constant initial y velocity the fountain looks terrible but why not have different initial velocities?

And the variable names of the code seem to mix up force with acceleration. E.g. "set velocity-x velocity-x + force-accumulator-x * step-size". Given that the particles do have different masses force and acceleration are different. Why not rename force-accumulator-x to acceleration-x?

The issue does not name a file or test; start by locating the Particle System Fountain model in the NetLogo Models Library and inspect its info tab and force-accumulator-x usage. Before changing it, clarify which physics behavior and controls are desired with maintainers. Done requires an agreed treatment of gravity and initial velocity, plus terminology that distinguishes force from acceleration.