Which statement best describes a joule?

• A. A unit of length
• B. A unit of force
• C. A unit of energy or work
• D. A unit of temperature

Answer: (C)

The joule is the unit used to measure energy or the amount of work done. It’s defined as one newton-meter: if you apply a force of one newton to move something one meter in the direction of the force, you’ve transferred one joule of energy (done one joule of work). Energy is the capacity to do work, and work is the transfer of energy through motion, so they share the same unit. The other options describe different quantities: length (meters), force (newtons), and temperature (Kelvin/Celsius).