Newton’s Second Law Simulation — Description
A red trolley sits on a 6 m runway. A blue arrow pushes it, and amber 1 kg blocks stacked on it are its mass. Pupils set the force (1–6 N) and the mass (1–3 kg) with two large stepper buttons, press Go, and watch the trolley accelerate from rest at a = F ÷ m until it reaches the chequered line. One line above the scene shows the sum: 4 N ÷ 2 kg = 2 m/s².
Every quantity is shown three ways at once — as a number, as the length of the arrow, and as the height of the stack — so a pupil who is not reading fluently can still predict which run will win. Sound carries it a fourth way: a click at each metre mark, arriving faster and faster because the trolley is accelerating.
By default each run races a pale ghost of the previous one in the back lane, which is where the comparison actually lands: same mass, more force, and it pulls away.
Using it in a lesson. Ranges are chosen so most whole-number pairs give whole-number answers, and every run lasts between 1.4 and 6 seconds. Two natural investigations: hold the mass and raise the force, then hold the force and raise the mass. Good before the dynamics-trolley required practical, or after it when the measurements have obscured the relationship.