Final answer:
The period of oscillation for a fluid in a U-tube cannot be determined without specific information about the system, and the provided references do not directly answer the question about using the energy method.
Step-by-step explanation:
The energy method for determining the period of oscillation of the fluid in a U-tube is not directly referenced in the provided information. Normally, the period of oscillation for a fluid in a U-tube could be found by considering the dynamics of the fluid motion and factors such as gravity and the characteristics of the fluid. Therefore, without specific information about the U-tube system or the method for finding the period, it's not possible to provide a concrete answer. The provided references are related to sound waves in tubes and do not offer a direct solution for finding the period of the fluid oscillation in a U-tube using the energy method stated in the question.