9.8:
Types of Collisions – II
The collision in a system whose momentum is conserved can be categorized as either elastic or inelastic, based on the nature of the interaction. A collision that leads to a decrease in the system's kinetic energy is termed an inelastic collision.
For instance, consider a collision between two asteroids. During the collision, the system constituted by the two asteroids may lose some of its kinetic energy as heat and light.
In case of a perfectly inelastic collision, however, the colliding objects suffer a maximum loss in kinetic energy and unite, resulting in the final kinetic energy of the system to become zero.
If a meteorite hits the Earth’s surface and comes to rest after the collision, then it is said to have lost all its kinetic energy while forming a crater on the surface. This also means that the particles constituting the system, the meteorite and the Earth, would stay together after the collision.
A collision in which the kinetic energy of a system increases is termed an explosion. For example, during a firecracker explosion, the chemical potential energy is converted to kinetic energy.
9.8:
Types of Collisions – II
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:
- A plastic ball dropped from a shelf, and it is unable to rise to its original height
- An accident between two vehicles on the road or a truck hitting a tree
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.