What is defined as the ability to do work?

The ability to do work is best defined as energy. In physics, work is done when a force applies to an object and causes it to move, and energy is the quantifiable capacity to perform this work. Energy comes in various forms, such as kinetic energy, potential energy, thermal energy, and more, and it is the fundamental concept that describes the potential to exert force over a distance, consequently accomplishing tasks.

For example, when you lift an object, you're using chemical energy from your body to do work against gravitational force, transforming that energy into gravitational potential energy. Thus, energy is fundamentally tied to the concept of doing work, making it the correct response to the question.

Other concepts like force and power, while related to work, do not define the ability to perform work directly. Force is a push or pull that can cause an object to accelerate, while power specifically quantifies the rate at which work is done over time. Voltage deals with electric potential difference, which is involved in energy transfer in electrical circuits but does not define the overall concept of work capacity.