Buildings in downtown Detroit with sunlight reflecting off the myriad windowpanes. (Field Mark Publications)

Work, in general, is an activity in which one exerts strength or faculties to do or perform something. In physics, work is defined as a force on an object multiplied by the displacement of the object. Measuring force in newtons (N) and displacement in meters (m) yields newtons times meters (Nm) as the units of work. To honor James Prescott Joule, who did pioneering work in the science of thermodynamics, a newton-meter is called a joule (J). A person pushing on a box with a force of 200 N (about 50 pounds) and moving the box 1 m would do 200 J of work. Energy is capacity, or ability, for doing work. Work and energy are both measured in joules.

After being outside on a cold day, a person's hand warms when shaking hands...