Science
Collisions.
Definition
Collisions occur when two or more objects exert forces on each other over a short time interval. In all collisions, total momentum is conserved. Collisions are classified as elastic (kinetic energy conserved) or inelastic (kinetic energy not conserved).
Examples
Real-world.
- 1 Billiard balls hitting each other approximate elastic collisions where both momentum and kinetic energy are conserved
- 2 A car crash is an inelastic collision—the vehicles crumple, converting kinetic energy to heat and deformation
- 3 Newton's cradle demonstrates conservation of both momentum and kinetic energy in elastic collisions
Key Fact
In all collisions: m₁v₁ᵢ + m₂v₂ᵢ = m₁v₁f + m₂v₂f (conservation of momentum).