Which of the following is a form of kinetic energy?

Kinetic energy is the energy of motion. Any moving object has KE: KE = ½mv². Examples: a moving car, falling water, wind, a thrown ball, atoms vibrating (thermal energy), electrons flowing (electricity). Forms of energy: (1) Kinetic — motion energy (mechanical, thermal, sound, electrical); (2) Potential — stored energy (gravitational, elastic, chemical, nuclear); (3) Radiant — electromagnetic waves (light, radio, X-rays). Energy conversions: (1) Falling object: gravitational PE → KE; (2) Pendulum: KE ↔ PE alternately; (3) Burning fuel: chemical PE → thermal KE → light + heat; (4) Battery → electrical current: chemical PE → electrical KE; (5) Photosynthesis: radiant → chemical PE in glucose. Conservation of Energy: energy cannot be created or destroyed, only transformed (First Law of Thermodynamics). The total energy of an isolated system is constant. In real systems, some energy is lost as heat (entropy increase — Second Law). 'Lost' energy isn't gone — it just becomes less useful (dispersed as low-grade thermal energy). Mechanical energy = KE + PE; in conservative systems (no friction), mechanical energy is conserved.