Inelastic collision
A collision in which kinetic energy is not conserved (though momentum is always conserved). Some kinetic energy is converted to other forms: heat, sound, deformation, breaking bonds. In a perfectly inelastic collision, the objects stick together after impact.
Formula
Σp conserved; KE lost = KE_before − KE_after
Real World
When two motorway vehicles collide and crumple together, investigators use conservation of momentum (not KE) to reconstruct pre-crash speeds from post-crash skid patterns.
Exam Focus
Momentum is always conserved in any collision — only kinetic energy is lost; stating 'energy is conserved' without qualification will lose marks.
How well did you know this?