Final answer:
Energy is mainly measured in calories and joules, with the joule being the SI unit of energy and the calorie commonly used in nutrition. One calorie is defined as 4.184 joules, making these units interchangeable based on context.
Step-by-step explanation:
Units of Energy
The standard units that are commonly used to measure energy are the calorie and the joule. The joule (J) is the SI unit of energy, defined as the amount of energy used when a force of 1 newton moves an object 1 meter. One joule is equivalent to 1 kilogram meter squared per second squared (1 kg m²/s²), which is also known as 1 newton-meter. On the other hand, a calorie (cal) is the amount of heat required to raise the temperature of 1 gram of water by 1°C. The calorie is especially familiar because of its use in nutrition to quantify the amount of energy in food; the nutritional Calorie (with a capital C, indicating kilocalorie) is equal to 1000 calories. To ensure uniformity, 1 calorie has been standardized to equal 4.184 joules.
Moreover, in context of electric energy, kilowatt-hour (kWh) is also used, particularly by power companies. When discussing work and energy, we should note that these concepts share the same units, as work is calculated as force multiplied by distance, resulting in energy units of joules. An understanding of energy units is crucial in various aspects of physics and engineering, as well as in understanding nutritional information.