Question

according to the law of conservation of energy, which statement must be true? a. the total energy of a system can decrease only if energy leaves the system. b. a system cannot take in additional energy. c. potential energy can only change to kinetic energy. d. there is only one form of energy.

Explanation:

The law of conservation of energy states that the total energy of an isolated system remains constant; energy can neither be created nor destroyed, only transformed or transferred.

• Option A: If energy leaves the system, the total energy of the system (which includes all forms of energy within it) will decrease, which aligns with the idea of energy transfer (leaving the system means the system's total energy reduces as energy is moved out).
• Option B: A system can take in additional energy (e.g., a system can absorb heat, which is energy, from its surroundings), so this is false.
• Option C: Potential energy can change to other forms too (e.g., potential energy can change to thermal energy due to friction, not just kinetic), so this is false.
• Option D: There are multiple forms of energy (kinetic, potential, thermal, electrical, etc.), so this is false.

Answer:

A. The total energy of a system can decrease only if energy leaves the system.