ABSTRACT

For material movement to occur, there must be a high-quality energy source out of which energy flows and a low-quality energy sink into which the energy flows. This energy flux makes mechanical work possible. Energy is recognized in two forms: potential energy, which is not associated with motion and gets stored in an object (e.g., a candy bar), and kinetic energy, which is any form of energy associated with motion, such as that found in a moving car. An estimate of the Earth’s global energy budget is illustrated in Figure 7.2. Not all of the energy that reaches the Earth is captured; even photosynthesis harvests only a small part of it (Figure 7.3).