# Collision in Physics | Definition, Examples, Types – Work, Energy and Power

Collision Physics Definition:
Collision between two or more particles is the interaction for a short interval of time in which they apply relatively strong forces on each other. In a collision, physical contact of two bodies is not necessary.

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## Collision in Physics | Definition, Types Physics – Work, Energy and Power

Types of Collision
There are two types of collisions
1. Elastic Collision Definition:
The collision in which both the momentum and the kinetic energy of the system remains conserved are called elastic collisions. In an elastic collision, all the involved forces are conservative forces and total energy remains conserved.

Elastic Collision Example:

• When a ball at a billiard table hits another ball, it is an example of elastic collision.

2. Inelastic Collision Definition:
The collision in which only the momentum remains conserved but kinetic energy does not remain conserved are called inelastic collisions. The collision in which two particles move together after the collision is called a completely inelastic collision.

In an inelastic collision, some or all the involved forces are non-conservative forces. Total energy of the system remains conserved. If after the collision two bodies stick to each other, then the collision is said to be perfectly inelastic.

Inelastic Collision Examples:

• The accident of two vehicles.
• When soft mudball is thrown against the wall, will stick to the wall.

Coefficient of Restitution or Resilience (e)
The ratio of relative velocity of separation after collision to the relative velocity of approach before collision is called coefficient of restitution or resilience. It is represented by e and it depends upon the material of the colliding bodies.

• For a perfectly elastic collision, e = 1
• For a perfectly inelastic collision, e = 0
• For all other collisions, 0 < e < 1

Work, Energy and Power:
Work, energy and power are the three quantities which are inter-related to each other. The rate of doing work is called power. An equal amount of energy is consumed to do a work. So, basically the power is the rate at which energy is consumed to complete a work.