Inelastic collisions are collisions between objects that do not conserve kinetic energy but do conserve momentum. They often occur between various molecules during chemical reactions.
Inelastic collisions also conserve energy. Since the law of conservation of energy states that energy cannot be created or destroyed, energy must be conserved during the collision. When two objects undergo an inelastic collision, they stick together and move as one unit in the direction of the object with the larger initial velocity. The overall final velocity is less than the initial velocities of the two colliding objects, but the momentum of the final objects is equal to their initial combined momentum.