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67 Cards in this Set
- Front
- Back
True or False. The term "fluid power" includes hydraulics and pneumatics, and is power that is applied through liquids or gases pumped or compressed to provide force and motion to mechanisms.
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True
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The prupose of your textbook, Fluid Power, is to provide you with ?
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A basic reference concerning fundamentals of fluid power
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What are the favorable characteristics of a fluid power system?
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very large forces can be controlled by much smaller ones, different parts of the system can be located at widely separated points, and motion can be transmitted without the slack inherent in the use of solid machine
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What type of system requires a medium amount of pressure and fairly accurate control?
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pneumatic
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What type of system requires a medium amount of pressure and more accurate control?
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combination hydraulic and pneumatic
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What type of system requires a great amount of pressure and/ or extremely accurate control?
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Hydraulic
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What are special problems of fluid power systems?
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loss in efficiency as the force of the fluid is conveyed up and down or around corners, loss of force as the fluid is transmitted over considerable distances, and leaks
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The Study of hydraulics was originally confined to the study of the physical behavior of water at rest and in motion. The term "hydraulics" now includes the physical behavior of all?
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liquids
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Pascal's law pertains to the?
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transmission of force in confined fluids
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True or False. All matter is classified according to its state as a solid, liquid, or a gas.
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True
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The critical factors affecting the state of matter are?
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pressure and temperature
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True or False. Pressure can be measured in terms of force per unit area.
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True
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True or False. The troposphere is that part of the atmosphere touching the earth's surface.
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True
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True or False. The atmosphere has weight.
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True
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True or False. Atmospheric pressure decreases as altitude decreases.
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False
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True or False. Atmospheric pressure at points below sea level is less then at sea level.
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False
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The reference standard used as an indicator of atmospheric pressure is a column of mercury that at sea level is?
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76 centimeters high at 0 degrees Celsius
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The side of a thin-walled chamber partially evacuated of air is the source of movement for the?
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aneroid barometer
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In the metric system the density of a substance is its weight in?
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grams per cubic centimeter
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What change, if any, will occur in the volume and weight of a substance if its temperature changes?
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its volume will change, but its weight will remain constant
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True or False. Specific gravity will vary with the size of the sample being tested.
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False
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How can the specific gravity of a liquid or solid be expressed?
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As a ratio between the weight of the substance and the weight of an equal volume of water or as the number that shows the density of the substance in the metric system
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What is the specific gravity of a liquid which weighs 44 pounds per cubic foot at 4 degrees C?
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0.705
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What is the density of a solid that has a specific gravity of 2.5?
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156 pounds per cubic foot
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What is the specific gravity of a solid object which weighs 49.92 pounds per cubic foot?
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0.8
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A device used for measuring the specific gravity of a liquid is known as a?
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hydrometer
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True or False. The pressure of force exerted on the end of a rigid metal bar is applied equally and undiminished to all surfaces of the bar.
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True
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The head, or pressure due to the weight of a fluid, depends on the density of the fluid and the?
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area of the bottom surface of the container
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Assume that the input piston has an area of 3 square inches with a force of 45 pounds. What is the pressure in the system?
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15psi
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Assume that the output piston has a diameter of 6 inches and is subject to a pressure of 10 pounds per square inch. What is the force exerted on the output piston?
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282.6
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For two pistons in the same fluid power system, the distances moved are inversely proportional to the?
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areas of the pistons
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In fluid power systems using liquids, the measurement of the volume of fluid flow is made in units of?
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gallons per minute
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Water flows through a pipe of 5 square-inch cross section at the velocity of 3 feet per second (fps). At what velocity does it flow through a constriction in the pipe with a cross section of 3 square inches?
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5.0 fps
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True or False. Two pistons with defferent cross-sectional areas will travel at the same speed as long as the rate of fluid flow into their cylinders is identical.
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False
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In streamline flow, each particle of fluid moves in what manner?
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in parallel layers
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True or False. Losses due to friction increase with velocity at a higher rate in turbulent flow than in streamline flow.
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True
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What is inertia of fluids in a power system?
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the resistance of the fluid to movement or change of rate of movement
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Neglecting friction, how much force is required to accelerate 3 pounds of fluid from rest to a velocity of 322 feet per second in 2 seconds?
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15 pounds
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True or False. Head is a statement of force per unit area.
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True
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True or False. Velocity head is the loss of energy caused by inertia.
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False
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True or False. Gravity head depends on which portions of the system are exposed to open air.
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False
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True or False. Friction head connot exist without velocity head.
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True
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True or False. There can be no static head if the fluid is in motion.
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True
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What factors affecting fluid action are classified as static factors.
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Gravity, atmospheric pressure, and applied forces
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The similarity between hydraulic and pneumatic fluid power systems is corrctly indicated by what statement?
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The basic components of the systems are essentially the same
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What component of a hydraulic fluid power system performs the same function as the receiver in a pneumatic fluid power system?
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reservoir
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Liquids rather than gases are used in hydraulic systems because liquids are?
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less compressible
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A liquid that is satisfactory for use in a hydraulic system provides?
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good lubrication and sealing qualities, and a viscosity that does not result in an increase in flow resistance in system piping
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True or False. The viscosity reading of a liquid is expressed as Saybolt universal seconds (SUS), which represents the time, in seconds, it takes for 60 cubic centimeters of the liquid at a specified temperature to pass through an orifice of given diameter.
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True
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A low V.I. indicates that a liquid will?
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Vary greatly in viscosity with changes in temperature
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True or False. Liquids derived from the same source have equal resistance to heat.
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False
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True or False. The film strength and lubrication qualities of a liquid are directly related to the liquid's physical properties.
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False
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What happens to hydraulic liquid that is continuously subjected to high temperature conditions?
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It changes unfavorably in composition
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Define fluidity.
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The physical property that enables liquids to flow
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Define viscosity.
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The internal resistance that tends to prevent liquids from flowing
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Define chemical stability.
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The ability of liquids to resist oxidation and deterioration for long periods
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The desirable flashpoint of a hydraulic liquid is one which provides a?
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low degree of evaporation and good resistance to combustion.
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Hydraulic liquid must possess what properties?
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chemical stability and freedom from acidity, lubricating ability and proper viscosity, and minimum toxicity and high flashpoint
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Although manufacturers strive to produce hydraulic liquids that contain non toxic chemicals, some liquids contain chemicals that are harmful. How do these poisonous chemicals enter the body?
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Absorption through the skin, through the eyes or mouth, or through inhalation
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The bases of the most common types of hydraulic liquids are classified as?
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water, petroleum, or synthetic
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What is the most widely used medium for hydraulic systems?
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petroleum-based liquid
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What properties of a hydraulic liquid can be improved by addititves?
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viscosity, chemical stability, lubricating power
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The fluid currently being used in a hydraulic system that requires a nonflammable liquid will proabably be a?
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synthetic-based liquid
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True or False. Synthetic based fluids contain toxic chemicals.
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True
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True or False. You have accidentally gotten a synthetic hydraulic fluid in your eyes. You should flush your eyes for at LEAST 15 minutes and seek immediate medical attention.
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True
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You are required to dispose of contaminated synthetic fluid while deployed. How should you dispose of the fluid?
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place it in drums for disposal ashore
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True or False. Water-based fluids' resistance to fire depends on the vaporization and smothering effect of steam generated from water.
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True
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