Final answer:
The statement is true; in a closed system that is completely mixed, the output is the same as the contents within the boundary. This aligns with principles of thermodynamics and conservation of energy.
Step-by-step explanation:
If a system is completely mixed, then it is reasonable to assume that the output from the system is the same as the contents within the system boundary. This statement is true. The example given discusses a well-insulated container in which a hot metal and cool water are mixed. Since the system does not exchange heat with its surroundings, it is a closed system. In this scenario, the final temperature of the mixed contents will be uniform, meaning that the output (in terms of temperature and heat content) will be the same as the mixture inside the system.
A closed (or isolated) system is one where the mass remains constant, and the net external force is zero. The total momentum of the system is conserved, and no energy enters or leaves the system. Thus, for a closed system that is mixed thoroughly, the output matches the internal state. This concept is essential in thermodynamics and understanding energy conservation in physical systems.