Final answer:
An elastic collision conserves both momentum and kinetic energy, whereas an inelastic collision conserves momentum but not kinetic energy. A perfectly inelastic collision is an extreme type of inelastic collision where objects stick together and lose maximum kinetic energy, but momentum is still conserved.
Step-by-step explanation:
A collision in which the total momentum and the total kinetic energy are conserved is called an elastic collision. These collisions are characterized by the fact that they do not result in any loss of kinetic energy, and they are quite rare in the everyday world because usually some energy is converted into other forms, such as heat or sound. By contrast, in an inelastic collision, the total momentum is conserved, but the total kinetic energy is not conserved. A special case of an inelastic collision is the perfectly inelastic collision, where the colliding objects stick together, causing a maximum loss of internal kinetic energy while still conserving momentum.
In summary, during an elastic collision, both momentum and kinetic energy are conserved, allowing final velocities to be calculated based on initial velocities and masses. During inelastic collisions, although momentum is still conserved, there is a change in internal kinetic energy, which is not conserved. Perfectly inelastic collisions are extreme cases where the objects stick together after collision, and kinetic energy is at its minimum post-collision, while momentum remains constant.