Key Concepts: Elastic & Inelastic Collisions

Elastic Collisions

• Both momentum and kinetic energy are conserved.
• Objects bounce off each other. No permanent deformation or heat generated.
• Example: billiard ball collisions (approximately), atomic/molecular collisions.

Inelastic Collisions

• Momentum is conserved, but kinetic energy is NOT — some KE is converted to heat, sound, or deformation.
• Most real-world collisions are inelastic.

Perfectly Inelastic Collisions

• Objects stick together after the collision. Maximum KE is lost.
• m₁u₁ + m₂u₂ = (m₁ + m₂)v_f → v_f = (m₁u₁ + m₂u₂)/(m₁ + m₂).

Comparing Collision Types

• Elastic: KE conserved, objects separate.
• Inelastic: KE lost, objects separate.
• Perfectly inelastic: Maximum KE lost, objects stick.