<P> An inelastic collision, in contrast to an elastic collision, is a collision in which kinetic energy is not conserved due to the action of internal friction . </P> <P> In collisions of macroscopic bodies, all kinetic energy is turned into vibrational energy of the atoms, causing a heating effect, and the bodies are deformed . </P> <P> The molecules of a gas or liquid rarely experience perfectly elastic collisions because kinetic energy is exchanged between the molecules' translational motion and their internal degrees of freedom with each collision . At any one instant, half the collisions are--to a varying extent--inelastic (the pair possesses less kinetic energy after the collision than before), and half could be described as "super-elastic" (possessing more kinetic energy after the collision than before). Averaged across an entire sample, molecular collisions are elastic . </P> <P> Although inelastic collisions do not conserve kinetic energy, they do obey conservation of momentum . Simple ballistic pendulum problems obey the conservation of kinetic energy only when the block swings to its largest angle . </P>

Where does lost energy go in inelastic collisions