When two or more objects collide with each other, they can stick together to form one single composite object (after collision). The total mass of the object after the collision is the sum of the masses of the original objects, and it moves with a velocity dictated by the conservation of momentum. Although the system's total momentum remains constant, the kinetic energy decreases, and thus such a collision is an inelastic collision. Most of the collisions between objects in daily life are inelastic in nature. Some examples of inelastic collision are:
In an inelastic collision, the final kinetic energy tends to decrease and remains lower than the initial kinetic energy of the system.
In some special cases, multiple objects collide, stick together, and remain motionless after the collision. Since the objects are all motionless after the collision, the final kinetic energy is also zero, and thus the loss of kinetic energy is at a maximum. This is a perfectly inelastic collision. For example, when a mud ball is thrown against the wall, it sticks to the wall and loses maximum kinetic energy.
This text is adapted from Openstax, University Physics Volume 1, Section 9.4: Types of Collisions.
