In pheesics, the kinetic energy o an object is the energy which it possesses due tae its motion. It is defined as the wirk needit tae accelerate a body o a gien mass frae rest tae its statit velocity. Havin gained this energy durin its acceleration, the body maintains this kinetic energy unless its speed chynges. The same amoont o wirk is duin bi the body in deceleratin frae its current speed tae a state o rest.
In classical mechanics, the kinetic energy o a non-rotatin object o mass m travelin at a speed v is ½ mv². In relativistic mechanics, this is anly a guid approximation when v is much less nor the speed o licht.