Inelastic Collision Calculator

Solve a stick-together collision

In a perfectly inelastic collision, two objects stick and share one final velocity. Momentum remains conserved during the isolated impact, but kinetic energy generally does not. This calculator divides total initial momentum by combined mass, then compares initial and final kinetic energies. It makes the energy conversion visible instead of incorrectly assuming that momentum conservation also preserves mechanical energy.

For a two kilogram object moving at three meters per second striking a one kilogram object at rest, the joined velocity is two meters per second. Initial kinetic energy is 9 joules, final kinetic energy is 6 joules, and 3 joules are lost from translational motion. That energy can become deformation, heat, sound, or internal motion.

Separate conserved momentum from lost kinetic energy

Velocities are signed along one dimension, and both masses must remain attached after impact. External impulse, rotation, rebound, fragmentation, and multidimensional geometry are excluded. The result is calculated in your browser. A negative energy-loss result would signal inconsistent arithmetic; with positive masses, the ideal stick-together model cannot increase translational kinetic energy on its own.