Final answer:
The statement regarding the restoration of normal hydraulic system 3 pressure and the handling of the landing gear selector valves is true. A hydraulic press requires a liquid to operate effectively and would not work properly with a gas. The normal reaction force is perpendicular to the surface of contact, not in the direction of gravity, making the statement false.
Step-by-step explanation:
Operation of Hydraulic Systems
If normal hydraulic system 3 pressure can be restored, stowing the manual gear release handle does indeed return the landing gear selector valves to normal operation. This statement is true. In a typical aircraft hydraulic system, the manual gear release handle is used to bypass the normal operation of the landing gear in cases where the hydraulic system fails to provide the necessary pressure. Once the system is restored, the handle can be reset, allowing the system to function under its normal, pressurized operations.
Hydraulic Press Operation with Gases
A hydraulic press operates on the principle of Pascal's law and is designed to work with incompressible fluids, such as hydraulic liquids. If a gas, which is compressible, is used instead, the press would not operate properly because gas compression would absorb some of the force that should be transmitted through the hydraulic system, leading to inefficiencies and potential failure to perform work as intended. Therefore, it is crucial to use a liquid in a hydraulic system.
Normal Reaction Force
The normal reaction is a force that is perpendicular to the surface of contact and does not act in the direction of the force of gravity. Therefore, the statement that the normal reaction acts in the direction of gravity is false. The normal reaction force often opposes the force of gravity but in a direction perpendicular to the point of contact with a surface.