Which of the following is an example of work not being done?

• A. Using mechanical force to push an object.
• B. Applying voltage to a circuit to move electrons.
• C. Using mechanical force to lift or move a weight.
• D. A compressed spring acting between two fixed objects.

Answer: (D)

The scenario involving a compressed spring acting between two fixed objects exemplifies work not being done because the spring is not moving either of those objects. In physics, work is defined as the transfer of energy that occurs when a force is applied to an object causing it to move in the direction of the force. For work to be done, there must be displacement in the direction of that force. In this case, although the spring is exerting force, if neither object is moving, there is no displacement and therefore, no work is being done.

The other options involve scenarios where mechanical force or voltage results in movement or displacement, which qualifies as work being done. For instance, using mechanical force to lift or move a weight directly correlates to work being performed as the weight is displaced against gravity, while applying voltage to a circuit facilitates the movement of electrons through the conductor, also constituting work due to the movement of charge.