We come across many types of collisions between different bodies in our daily lives like the collision between a bat and ball a scooter and a truck moving in opposite directions and the collision between a striker and coins in a game of carom etc. In the subatomic world, there may be collisions between various subatomic particles such as protons, electrons and neutrons.
In any collision, the linear momentum of the system is conserved. we can say that the total change In momentum during a collision is zero or we can say that the total momentum of the system is conserved during collisions.
There are three different kinds of collisions they are elastic collision, inelastic collision and completely inelastic collision.
In a collision, if both the total momentum (P), and total kinetic energy (KE), of the colliding bodies is conserved, then it is an elastic collision. In such a collision, the bodies move separately after the collision and the loss in kinetic energy, DKE, is zero. This implies that there is no loss in kinetic energy. For example, the collision between subatomic particles is an elastic collision.
In a collision, if only the total momentum of the colliding bodies is conserved and not the kinetic energy, and the colliding bodies move separately after the collision, then the collision is called an inelastic collision. There is some loss in kinetic energy of the system during this collision. This implies that delta KE is not equal to zero. For example, the collision between billiard balls is an inelastic collision.
In a collision, if only the total momentum of the colliding bodies is conserved and the total kinetic energy is not conserved, and the bodies stick together after the collision, then it is a perfectly inelastic collision. There is maximum loss of kinetic energy during this collision. This implies that delta KE is maximum.
For example, the collision between a clay ball and a metallic ball is a perfectly inelastic collision.
In a nuclear reactor, to increase the probability of the fission of uranium, the material must absorb neutrons with relatively low kinetic energies called slow neutrons. But neutrons released during nuclear fission have relatively high kinetic energies and are called fast neutrons.
To slow down these fast neutrons and convert them into slow neutrons, they are forced to collide with atoms of a material known as a moderator. Usually, graphite is used as a moderator.
In a real life situation, we do not encounter collisions where bodies, before and after colliding, move along the same straight path.
They collide in two dimensions, as usually observed in a game of billiards or carom.