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Pressure is the force per unit of area |
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within a fluid the forces are created by
molecular collisions |
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the area is the surface area of the container |
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pressure is measured in: |
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psi (lbs/in2) |
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pascals (N/m2) |
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atmospheres |
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in.of Hg or mm of Hg |
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Atmospheric pressure = |
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14.7 psi |
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or 101.3 kPa |
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or 1 atm. |
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or 30 in. of Hg or 760 mm of Hg |
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Gas laws |
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Absolute temperature and pressure |
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General gas law |
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Boyle’s law |
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Charles’ law |
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Density |
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mass density (metric) |
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weight density |
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specific gravity - ratio of the density of the
substance to the density of water |
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adhesion - attraction between unlike molecules |
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cohesion - attraction between like molecules |
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surface tension - due to cohesive forces in
fluid when the shape is changed |
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capillary action - due to adhesive forces and
the surface tension |
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Viscosity - the internal resistance of a fluid |
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Pressure - may be due to the weight (density) of
a fluid and the depth. |
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- an object in a fluid is buoyed up with a force
equal to the weight of the fluid displaced |
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Buoyancy - apparent weight difference of an
object submerged in a liquid due to the pressure difference from top to
bottom |
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Pascal’s principle - pressure applied to an
enclosed fluid is transmitted undiminished to every portion of the fluid
and to the walls of the container |
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Flow is
the result of a pressure difference. |
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Assumptions: |
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Streamline (laminar) vs. turbulent |
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incompressible |
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nonviscous |
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Flow rate (F ) |
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The total energy per unit of volume (pressure)
of a fluid must remain constant |
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if speed increases,…pressure decreases |
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venturi effect |
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if speed decreases,… pressure increases |
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Passive transport |
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diffusion |
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osmosis |
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gravity |
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dialysis |
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Active transport |
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movement against the natural flow due to
pressure and concentration of fluids requires external forces and energy |
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The heart (pump) |
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Pressure differences |
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velocity and cross-sectional area changes in
veins and arteries |
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gravitational effects on pressure and flow rate |
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Pressure vs. volume in the lungs |
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diffusion through the membranes |
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surface tension in the alveoli |
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Notes