The kinetic energy of an object is the extra energy which it possesses due to its motion.
The adjective "kinetic" has its roots in the Greek word κίνηση (kinesis) meaning "motion" – the same root as in the word cinema (referring to motion pictures).
The principle in classical mechanics that E ∝ mv² was first theorized by Gottfried Leibniz and Johann Bernoulli, who described kinetic energy as the "living force", vis viva. Willem 's Gravesande of the Netherlands provided experimental evidence of this relationship. By dropping weights from different heights into a block of clay, 's Gravesande determined that their penetration depth was proportional to the square of their impact speed. Émilie du Châtelet recognized the implications of the experiment and published an explanation.[1]