The joule, symbol J, is the unit of energy in the science community. It is not widely used outside the science community in the United States, but it is elsewhere. For example, in the United States, the energy content of a food product is likely expressed in food calories. This energy could be expressed in joules, and that is being done in many parts of the world. A Diet Coca Cola in Australia is labeled Low Joule rather than Low Cal as in the United States. To obtain a feeling for the size of a joule, consider the following statistics:

• the sound energy that is in a whisper is about 0.01 joules,
• the kinetic energy of a 1,000-kilogram car traveling 25 meters per second (55 miles per hour) is about 300,000 joules,
• the energy from burning a barrel of oil is 6,000,000 joules,
• the annual energy use in the...