# Collision summary

Collision

A collision refers to the interaction between two or more objects, during which they exert forces on each other for a relatively short period. Collisions can occur between particles, such as billiard balls or atoms, or between macroscopic objects, like cars or celestial bodies.

Types of Collisions:

1. Elastic Collision:

• In an elastic collision, both kinetic energy and momentum are conserved.
• The total kinetic energy before and after the collision remains the same.
• Elastic collisions often occur at the molecular or atomic level.
2. Inelastic Collision:

• In an inelastic collision, only momentum is conserved, not kinetic energy.
• The total kinetic energy of the system decreases after the collision.
• Inelastic collisions are common in macroscopic objects like cars.

Elastic Collision Equations:

1. Conservation of Momentum:

• The sum of momenta before the collision is equal to the sum of momenta after the collision.
• For two objects: ${m}_{1}{u}_{1}+{m}_{2}{u}_{2}={m}_{1}{v}_{1}+{m}_{2}{v}_{2}$
• Where is m mass, is initial velocity, and is final velocity.
2. Coefficient of Restitution (e):

• It quantifies the "bounciness" of the collision.
• For a perfectly elastic collision, , and for a perfectly inelastic collision, .

Inelastic Collision Equations:

1. Conservation of Momentum:

• As in elastic collisions, momentum is conserved in inelastic collisions.
2. Coefficient of Restitution (e):

• In inelastic collisions, 0 < e < 1
• can be used to determine the degree of deformation or "stickiness" during the collision.

Real-life Applications:

• Road traffic accidents (inelastic collisions).
• Particle collisions in particle accelerators (high-energy physics).
• Billiards and other sports (elastic collisions).