Question

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

Explanation:

The law of conservation of energy states that energy cannot be created or destroyed, only transferred or transformed. Option A is wrong as potential energy can change into other forms like thermal energy too. Option B is incorrect since a system can take in energy. Option D is false as there are multiple forms of energy such as kinetic, potential, thermal etc. Option C is in line with the conservation - energy can only decrease in a system if it leaves the system.

Answer:

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