Grade 12 · Theory
Elastic and inelastic collisions
Momentum and impulse · about 3 min
Visual overview: Elastic and inelastic collisionsAll collisions conserve momentum, but only elastic ones conserve kinetic energy.
Key points- Elastic: both momentum AND kinetic energy are conserved.
- Inelastic: momentum is conserved, kinetic energy is not (some becomes heat and sound).
- Test by calculating total Ek before and after: Ek = ½mv².
- Objects sticking together always indicates an inelastic collision.
- Elastic collision — kinetic energy conserved.
- Inelastic collision — kinetic energy lost.
EXAM TIP
show both kinetic energy totals and compare them explicitly — a claim without the calculation earns nothing.