Kinetic Energy, Energy-Work Principle

Kinetic energy

In physics, kinetic energy is the energy of an object due to the motion of the object. It equals to the work needed to accelerate that object from rest to its stated velocity. Just as any other energy, it has the SI unit of joule (J).

The kinetic energy of a non-rotating object is

$$E_k=\frac{1}{2}mv^2$$

where $m$ is the mass of the object, and $v$ is the speed of the object.

Because the momentum of an object

$$\vec{p}=m\vec{v}$$

the kinetic energy also equals to

$$E_k=\frac{p^2}{2m}$$

Kinetic energy and work

Work-energy principle states that the work done by all forces acting on an object equals to the change in kinetic energy of the object.

$$W=\Delta E_k$$