What does the term "work done" refer to in a physical context?

The term "work done" in a physical context specifically refers to the process where a force acts on an object to move it over a distance. In physics, work is mathematically defined as the product of the force applied to an object and the distance over which that force is applied, given that the force and the movement are in the same direction. This definition links the concepts of energy and motion, emphasizing the role of force in achieving movement.

Considering the other options, the first option, about energy expended during sleep, does not relate to the physical definition of work done, as it does not involve a force acting on an object to cause movement. The third option, which mentions a measure of time spent exercising, also strays from the concept of work done, as time alone does not account for the force or distance. Lastly, the total number of repetitions completed refers to an amount of activity but not to the physical movement defined as work done. Therefore, option B accurately captures the core principle of work as described in physics.