Collision

A collision between two particles is said to occur if they physically strike against each other or if the path of the motion of one is influenced by the other. In physics, the term collision does not necessarily mean that a particle actually strikes. In fact, two particles may not even touch each other and yet they are said to collide if one particle influences the motion of the other.

When two bodies collide, each body exerts a force on the other. The two forces are exerted simultaneously for an equal but short interval of time. According to Newton's third law of motion, each body exerts an equal and opposite force on the other at each instant of collision. During a collision, the two fundamental conservation laws namely, the law of conservation of momentum and that of energy are obeyed and these laws can be used to determine the velocities of the bodies after collision. The assumption of conservation of momentum as well as the conservation of kinetic energy makes possible the calculation of the final velocities in two-body collisions.

Collisions are divided into two types :

• Elastic Collision
• Inelastic Collision

A perfectly elastic collision is defined as one in which there is no loss of kinetic energy in the collision. An inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision.

Types of attack by means of a deliberate collision include:

With the body: unarmed striking, punching, kicking, martial arts, pugilism

Striking directly with a weapon, such as a sword, club or axe

Ramming with an object or vehicle, e.g.

A car deliberately crashing into a building to break into it

A battering ram, medieval weapon used for breaking down large doors, also a modern version is used by police forces during raids

An attacking collision with a distant object can be achieved by throwing or launching a projectile.