Collisions Lab — Momentum Conservation and Kinetic Energy in Elastic and Inelastic Collisions
This interactive physics simulation uses the Matter.js rigid-body engine to demonstrate collisions between objects on a frictionless one-dimensional rail and in a free-roaming two-dimensional sandbox. Users can adjust mass, launch velocity, and the coefficient of restitution to directly observe that linear momentum is always conserved in a collision, while kinetic energy is only conserved in the perfectly elastic case — the gap between elastic and inelastic collisions is displayed live as a percentage of kinetic energy lost.
A center-of-mass marker demonstrates that the center of mass of an isolated two-body system moves at constant velocity before, during, and after a collision, regardless of how elastic or inelastic that collision is — a foundational result in introductory mechanics courses covering linear momentum, impulse, and collisions.
Keywords: collision simulation, momentum conservation demo, elastic collision calculator, inelastic collision physics, kinetic energy loss, center of mass physics, Matter.js physics engine, physics education tool