Work-Energy Theorem

Let's look at how energy is related to work. As already mentioned, we distinguish two basic kinds of energy:

Kinetic Energy K - Energy of motion
Potential Energy U - Energy of position, stored energy.

The kinetic energy of an object is defined as

K =

m v²

where K is the kinetic energy, m is the mass of the object, and v is the velocity of the object. Since the mass is a positive number, this means that the kinetic energy is always larger than or equal to 0.

The relationship between work and the change in kinetic energy $\Delta$K is

W = $\Delta$K

This is known as the work-energy theorem.

The basic physical statement of the work-energy theorem is: When an object is in motion, it has the capacity to do work.

Pretty soon, once we have taken a more detailed look at potential energy, U, we will extend the work energy to also include the potential energy, and our theorem will read:

W = $\Delta$K + $\Delta$U