3–42. What is the principle function of the globe valve? 1. To protect the cylinder from excessive  pressure 2. To prevent the liquid in the reservoir  from  flooding  the small  cylinder 3. To make possible several short strokes instead of one long stroke with the piston 4. To allow the fluid in the large cylinder   to flow back into the reservoir 3–43. A main ballast tank on a submarine is 1. 2. 3. 4. filled with sea water by allowing air to escape from the vents at the top of the tank and allowing water to enter through flood ports at the bottom of the tank pumping air from the tank and pumping water into the tank through the vents at the top pumping it in through the vents at the top of the tank pumping it in through the ports at the bottom of the tank 3-44. How is the water removed from the main  ballast  tanks  when  a  submerged submarine  is  surfacing? 1. Motor–driven  pumps  syphon  off the water 2. The water is forced out with high–pressure  air 3. The water flows out through ports under the pull of gravity 4. Hydraulic pumps syphon off the water 3–45. The variable ballast tanks on a submarine are filled with sea water by 1. 2. 3. 4. allowing air to escape from the tanks and water to enter through flood ports at the bottom of the tanks pumping air from the tanks and allowing the water to enter through vents at the top of the tanks either of the above methods pumping it in 3–46. Hydraulic  machines  are  used  aboard submarines  for 1. opening  and  closing  the  vent valves  of  the  main  ballast tanks 2. raising and lowering the periscope 3. opening  and  closing  the  vent valves of the safety tanks 4. all of the above purposes When answering items 3–47 and 3-48, * refer to figure 10–14 of your textbook. 3–47. The the 1. 2. 3. 4. purpose of an accumulator in hydraulic system is to accumulate oil as it is released  from  the  reservoir keep the air in the system at a constant  pressure accumulate  excess  oil  which flows past check valves in the system keep the oil in the system under  pressure 3–48. To what part, if any, is the piston in  the  accumulator  fastened? 1. A rod which is operated by a crankshaft 2. A rod which is activated by pressurized oil in the reservoir 3. A main flood valve 4. None 3-49. Why is it easier to push a 50–pound barrel up a gangplank than to push a 50 pound box? 1. Rolling friction is less than a sliding  friction 2. The shape of a barrel defies gravity better than the shape of a box 3. The barrel has a greater surface to come in contact with the gangplank 4. All of the above reasons 28