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34 Cards in this Set
- Front
- Back
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What is a fluid?
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Something that flows (gas, vapor, liquid)
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What is pressure?
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Force per unit area (P = force / area)
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What is the SI unit of pressure?
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Pasals
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What is one pascal?
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1 Pascal = 1 Newton / Meter squared
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1 atm = ? mmHg
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760 mmHg
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1 atm = ? lb/in2
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14.7 lb/in2
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1 atm = ? bar
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1.013 bar
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1 atm = ? torr
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760 torr
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1 atm = ? Pascals
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1.013 x 10^5 Pascals
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What is Pascal's Law?
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Pascal's Law is that pressure applied to an enclosed fluid is transmitted eequally in all directions and to all parts of the enclosing vessel, *if* pressure changes due to the weight of the fluid may be neglected.
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At what angle does fluid exert forces on the container?
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At right angles to the force of gravity
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Describe the force exerted by a single particle within a fluid
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The force exerted is the same in all directions at a given depth
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How does the surface of a liquid relate to the force of gravity? other forces?
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The surface of a liquid will always be perpendicular to the net forces acting on it (e.g. gravity.) However, certain forces (spinning) will cause it to form other shapes (e.g. a parabola)
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Is the pressure of a fluid equal at any given depth?
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No, because additional pressure is exerted by the weight of the fluid above any given point
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What is the pressure at a given height (H) in a fluid column of a fluid of a given density (D)
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Pressure *due to weight of fluid above it* = Density x Gravity (9.8 m/s/s) x Height
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How is height measured in diagonal fluid columns
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Height is always measured along the axis which gravity pulls (i.e. straight down), not along the long axis of the pipe.
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What is the specific gravity of mercury
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13.6 (i.e. mercury is 13.6 times more dense than water.)
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What is the absolute pressure at a given depth?
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Pressure = Density x Gravity (9.8m/s/s) x Height + External pressure
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Does the pressure at the bottom of a fluid filled container change at sea level and high in the mountains?
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Yes, because the external pressure changes.
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What is gauge pressure?
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Gauge pressure is the *difference* between an unknown pressure and atmospheric pressure
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What is normal atmospheric pressure?
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1 atm = 760 mmHg = 14.7 lb/in2 = 1.013 bar = 1.013 x 10^5 pascals
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What is absolute pressure?
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True pressure. Absolute pressure = gauge pressure + atmospheric pressure
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What causes atmospheric pressure?
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The weight of the air above the earth
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What is archimedes principle?
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A body immersed in fluid is buoyed up by a force equal to the weight of the displaced fluid (i.e. the body looses weight equal to the amount of fluid it displaces)
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Does archimedes principles apply only to floating bodies, or to submerged bodies as well?
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To both
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What is the explanation of archimedes principle?
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As fluid is displaced, it increases the height of the fluid column. This causes additional pressure (P = DGH), evenly distributed, which pushes back up on the object.
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What makes an object buoyant?
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If the upward force on the object (by the fluid) is greater than or equal to the downward force of gravity
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What is the buoyant force acting on any object?
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The weight of the water displaced by the object
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Why does a heavilly laden ship float?
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Its total weight equals exactly the weight of the water it displaces. As the weight increases, the mass of water displaced increases, and the buoyant force increases.
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What is a center of buoyancy?
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The point at which the net buoyant forces act.
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What relationship of center of gravity and center of buoyancy makes a ship most stable?
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When they are far apart
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How can the volume of an irregularly shaped object be determined?
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By weighing an object in air and then submersed in water, the difference in weight is equal to the volume of water displaced. Since water has a known density, its volume may be determined.
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What is a hydrometer?
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A graduated glass or metal instrument used to measure either the specific gravity or density of a liquid. A float of a known density is placed in the liquid, and based on its buoyancy, the density of the liquid is determined.
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What are hydrometers used for?
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MEasuring density or purity in storage batteries, ship boilers, soil and milk.
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