Conservation of Momentum

• An inelastic collision is a collision in which kinetic energy is not conserved due to the action of friction, but the total momentum and energy are conserved. 
• Kinetic energy had been transferred to some other forms of energies. In collisions of macroscopic bodies, some kinetic energy is turned into vibrational energy of the atoms, causing a heating effect, and the bodies are deformed. A usual characteristic of inelastic collision is that object stick together after collision.

An elastic collision is an encounter between two bodies in which the total kinetic energy of the two bodies remains the same. In an ideal, perfectly elastic collision, there is no net conversion of kinetic energy into other forms such as heat, noise, or potential energy.