Kinetic Energy

Kinetic energy is the energy an object has because of its motion. For an object of mass m moving at speed v, E_k = ½mv², measured in joules.The equation comes from the work done to accelerate the object. A constant force F accelerates a mass from rest over a distance s, so the work done is Fs = mas. Since v² = 2as for an object starting from rest, the work done is ½mv², and this is the kinetic energy gained.Kinetic energy is proportional to the square of the speed. Doubling the speed makes the kinetic energy four times larger, and doubling the kinetic energy increases the speed by a factor of √2.Kinetic energy is a scalar, so it has no direction and is never negative. In energy problems it is often transferred to or from gravitational potential energy or elastic potential energy, or dissipated as heat by friction.