Colin Donnelly-
Fluids
Fluids are substances that have the ability to flow and conform to the shape of their containers.
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Fluids can exert _____ forces, but cannot exert _____ forces.
perpendicular
shear
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_____ and _____ are the two phases of matter that are fluids.
Liquids and gases
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Solids
Solids do not flow and they retain their shape regardless of their containers.
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Density
Density is the mass per unit volume of a substance (fluid or solid).
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Pressure
Pressure is defined as a measure of force per unit area.
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Pressure is exerted by a fluid on _____ and on _____.
the walls of its container
objects placed in the fluid
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Pressure is a _____ quantity
scalar
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The pressure exerted by a gas against the walls of its container will always be _____ to the container walls.
perpendicular (normal)
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Absolute pressure
Absolute pressure is the sum of all pressures at a certain point within a fluid
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Absolute pressure is equal to _____ plus _____.
the pressure at the surface of the fluid (usually atmospheric pressure)
the pressure due to the fluid itself
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Gauge pressure
Gauge pressure is the name for the difference between absolute pressure and atmospheric pressure.
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In liquids, gauge pressure is caused by ...
... the weight of the liquid above the point of measurement.
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Pascal’s principle
Pascal’s principle states that a pressure applied to an incompressible fluid will be distributed undiminished throughout the entire volume of the fluid
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Hydraulic machines
Hydraulic machines operate based on the application of Pascal’s principle to generate mechanical advantage.
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Archimedes’ principle
When an object is placed in a fluid, the fluid generates a buoyant force against the object that is equal to the weight of the fluid displaced by the object.
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The direction of the buoyant force is always ...
... opposite to the direction of gravity.
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If the maximum buoyant force is _____, the object will float. This will be true if the object is _____ than the fluid it is in.
larger than the force of gravity on the object
less dense
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If the maximum buoyant force is _____, the object will sink. This will be true if the object is _____ than the fluid it is in.
smaller than the force of gravity on the object
more dense
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Cohesive forces
Fluids experience cohesive forces with other molecules of the same fluid.
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Adhesive forces
Fluids experience adhesive forces with other materials.
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Cohesive forces give rise to _____.
surface tension
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Fluid dynamics
Fluid dynamics is a set of principles regarding actively flowing fluids.
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Viscosity
Viscosity is a measurement of a fluid’s internal friction.
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Viscous drag
Viscous drag is a nonconservative force generated by viscosity.
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Fluids can move with either _____ or _____.
laminar flow or turbulent flow.
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The rate of laminar flow is determined by the relationships in _____.
Poiseuille’s law
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On the MCAT, incompressible fluids are assumed to have _____ and _____ while flowing, allowing us to assume _____.
laminar flow and very low viscosity
conservation of energy
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Continuity equation
The continuity equation is a statement of the conservation of mass as applied to fluid dynamics.
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Bernoulli’s equation is an expression of _____ for a flowing fluid.
conservation of energy
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Bernoulli’s equation
Bernoulli’s equation states that the sum of the static pressure and the dynamic pressure will be constant between any two points in a closed system.
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For a horizontal flow, there is an _____ relationship between pressure and speed.
inverse
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Venturi effect
In a closed system, there is a direct relationship between cross-sectional area and pressure exerted on the walls of the tube known as the Venturi effect.
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The circulatory system behaves as a _____ with _____ flow.
closed system
nonconstant
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Resistance _____ as the total cross-sectional area increases.
decreases
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Arterial circulation is primarily motivated by _____.
the heart
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Venous circulation has _____ the volume of arterial circulation.
three times
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Venous circulation is motivated by _____.
the skeletal musculature and expansion of the heart.
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Inspiration and expiration create a pressure gradient not only for the _____, but for the _____ as well.
respiratory system
circulatory system
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Air at the alveoli has _____.
essentially zero speed
