The Law of Conservation of Energy states that energy cannot be created or destroyed. Which statement describes this law?

• A. Energy is destroyed by friction
• B. Energy is created when work is done
• C. Energy cannot be created or destroyed
• D. Energy is conserved only in ideal systems

Answer: (C)

The main idea here is that energy can change form, but the total amount stays constant in a closed system. In real situations, energy shifts between kinetic, potential, heat, sound, and other forms. When something slows due to friction, its kinetic energy decreases, but that energy isn’t lost—it becomes thermal energy in the surroundings. So the statement that energy cannot be created or destroyed best captures what the law says.

The other ideas don’t fit because friction doesn’t destroy energy; it just transforms it. Work doesn’t create energy from nothing; it transfers energy into or out of a system. And conservation applies in real life too, not only in idealized scenarios—even with non-idealities, all forms of energy are accounted for, and the total remains constant.