Momentum and Collisions
Momentum (p): p = mv (mass × velocity). Measured in kg·m/s.
Conservation of momentum: In a closed system (no external forces), total momentum before = total momentum after any collision.
m₁v₁ + m₂v₂ = m₁v₁' + m₂v₂'
Elastic collision: Kinetic energy conserved; objects bounce off each other (ideal billiard balls).
Perfectly inelastic collision: Objects stick together; kinetic energy is not conserved (some becomes heat/deformation).
Impulse: Change in momentum = F × t. Increasing impact time reduces peak force — why airbags and crumple zones save lives.