Work and Energy

The concepts of work and energy exist in our daily lives. In terms of physics, energy is the capacity to do work. We will elaborate further on this in the following sections of this chapter.

Energy exists in many forms. We will learn that the two of the main categories are kinetic energy (= energy of motion) and potential energy (= energy of position). There are several main classes of potential energy: Mechanical, Chemical, Electrical, Nuclear, ...

We will also learn that total energy is conserved for an isolated system. This means that energy can be converted from one form to another, but the total energy (= sum of all different energy forms) does not change.

The concepts of work and energy will give us elegant methods of working problems that would be very complicated using kinematics and dynamics.

The SI-unit of work (and energy) is the Joule (J).

1 J = 1 N$\cdot$m = 1 kg$\cdot$m2/s2

The dimensionality of work is \[ \rm \mathbf{[W] = \frac{[M][L]^{2}}{[T]^{2}}} \]

Many other energy units are in use. To make your life easier when you try to convert from one energy unit to another, we have provided a handy unit conversion engine.

© MultiMedia Physics, 1999