Why learn about the conservation of energy?

One of the most important principles in physics is conservation of energy, which tells us that the total energy is constant in any process. The energy within a system may be changed from one form to another or be transferred from one system to another, but the total amount of energy remains the same. Because all physical processes involve energy, conservation of energy gives us an incredibly powerful way to think about and solve physics problems.

In terms of solving problems, there usually isn’t any difference between using the Work-Energy Theorem and using the Conservation of Energy equation. Both equations help us keep track of how the energy of a system is rearranged as it evolves from one state to another. But conservation of energy points to a more fundamental truth about the physical world, that you cannot just create energy out of nothing or make it disappear. This idea, that energy has to come from somewhere and has to go somewhere if you try to get rid of it, has major implications for the systems we build and use every day.