Joules are units of

• A. units of energy
• B. units of force
• C. units of charge
• D. units of work

Answer: (D)

Joules measure the amount of energy transferred when a force moves something a certain distance. In physics, work is defined as the energy transferred by applying a force over a distance, so the unit used to quantify that transfer is the joule. One joule equals one newton–meter (1 J = 1 N·m). For example, lifting a 2-newton weight by 0.5 meters uses 1 joule of work (2 N × 0.5 m = 1 J). Because work is a form of energy transfer, the joule serves as the unit for that quantity as well. While we often talk about energy in joules, the same unit applies to work, which is why joules are described here as units of work.