41 Introduction to Work, Energy, and Energy Resources

Energy is everywhere. It fuels the human body, powers machines, drives the climate, and underlies every physical process in nature. Whether we are talking about the chemical energy in food, the mechanical energy used to ride a bicycle, or the radiant energy from sunlight, energy is a central concept in science—and in our everyday lives.

In physics, energy is a fundamental quantity that is deeply tied to the behavior of matter and forces. While there is no single, simple definition that captures all aspects of energy, we can loosely define it as:

Energy is the ability to do work.

This definition is a starting point, but as we will see, not all energy is immediately available to do work. Nonetheless, this association helps us explore energy through measurable, physical processes.

The Conservation of Energy

One of the most powerful and universal ideas in science is the law of conservation of energy, which states:

Energy cannot be created or destroyed. It can only be transformed from one form to another or transferred between systems.

This principle has been validated across centuries of experiments, from early studies of mechanical systems to the discovery of nuclear energy. Even when new forms of energy are discovered—such as thermal energy, electrical energy, or nuclear energy—the total amount of energy in the system remains unchanged.

A striking extension of this principle came from Albert Einstein, who proposed that mass itself is a form of energy. His famous equation,

[latex]E = mc^2[/latex]

shows that mass [latex]m[/latex] and energy [latex]E[/latex] are equivalent, with [latex]c[/latex] being the speed of light. This insight connects energy to the very fabric of matter.

Energy in Society

Beyond the scientific framework, energy has enormous importance in society. Our modern world depends on the availability of energy resources—fossil fuels, electricity, solar, wind, and more—to power industries, heat homes, run hospitals, and transport goods. The global demand for energy continues to rise, raising complex issues related to:

• Economic development

• Environmental sustainability

• Political stability

• Public health and climate change

An understanding of energy—from its physical principles to its real-world impacts—is essential for informed decision-making in science, engineering, healthcare, and policy.

Why Study Work Before Energy?

Since energy is related to the ability to do work, our study begins with the concept of work in a physics context. Work involves a force acting on an object to cause displacement. It provides a bridge between forces (which we’ve already studied) and energy (which we are about to explore in depth).

Through work, we will understand how energy moves between systems or changes from one form to another—such as from chemical energy in food to mechanical energy in muscle motion, or from gravitational potential energy to kinetic energy in a falling object.