Which statement about energy cannot be created or destroyed?

• A. Energy can be created
• B. Energy can be destroyed
• C. Energy doubles in a closed system
• D. Energy cannot be created or destroyed

Answer: (D)

Energy is conserved in a closed system. It can change from one form to another, but the total amount stays the same. That means energy cannot be created from nothing or destroyed; it simply shifts between forms like kinetic, potential, thermal, electrical, and light. A pendulum is a good illustration: as it rises, kinetic energy becomes potential energy, and as it swings down, potential becomes kinetic, with the total energy remaining constant. A lamp also shows this idea—electrical energy is transformed into light and heat, not created or destroyed.

From that perspective, the statement that energy cannot be created or destroyed is the right one. The idea that energy can be created would violate conservation by introducing new energy, and the idea that energy doubles in a closed system would imply energy is being generated, which again contradicts conservation.