Physics Chapter 5: Fluids Flashcards
Poiseuille’s law (in relation to Q)
Q = flow rate. Applies to laminar flow, accounting for viscosity
Poiseuille’s law (in relation to P)
Applies to laminar flow, accounting for viscosity
Continuity Equation
Within a closed system, the flow rate of a liquid is constant
Narrower tube has a _________ velocity and _________ pressure
Higher, lower
Narrower tube has _________ pressure
Lower
Higher velocity means __________ pressure
Lower
Venturi effect describes what relationship
Narrower tube = lower pressure
Archimedes principle
Flow Rate
Volume of fluid passing by a specific point per unit time Q = A*v
Poiseuille’s Law definition
describes the flow rate of a fluid through a cylindrical pipe under laminar (smooth) flow conditions
What does the heart do when blood vessels constrict
it has to pump harder to maintain pressure because according to Poiseuille’s law, pressure change and radius are inversely proportional
1atm = ____ kPa = ______ mmHg
101 kPa, 760mmHg
Fluid pressure changes with depth are assumed to be linear. Why isn’t this the same for atmospheric pressure?
Volume of air isn’t constant.
Hydrostatic pressure for liquids is linear because as depth changes, the density of the liquid remains relatively constant. Gases, however, are compressible, so volume is affected by changes in pressure.
Formula for density
Density of water
Specific Gravity
Basic formula for pressure
P = F/A
Pressure when submerged in a fluid
Absolute Pressure
Gauge Pressure
% of object submerged
Archimede’s principle
Mechanical advantage of a hydraulic lift
Idea is that the same volume of fluid is being moved, force necessary depends on area
What is surface tension?
caused by uneven intermolecular interactions @ interface between 2 surfaces (adhesive and cohesive forces)
If adhesive forces to wall of a container are stronger than cohesive forces within a molecule what happens?
concave meniscus (water)
If cohesive forces within a molecule a are stronger than cohesive forces to the walls of a container what happens?
Convex meniscus (mercury)
Viscosity
Resistance to flow (resistance to deformation by stress)
Bernoulli’s law
Applies to ideal fluids with laminar flow and NO viscosity
Continuity equation is due to
the incompressibility of liquids
Pitot tube can be used to calculate what?
Velocity of a fluid
What is this an example of?
The oxygen pressure is the sum of the oxygen static pressure P and the oxygen flow pressure ½ ρv2. In the area of the mask openings, Pair = P + ½ ρv2, thus Pair > P. Air enters the mask because the static pressure of the air is larger than the static pressure of the oxygen that flows in the mask. This is the Venturi effect, and the mask is called the Venturi mask.
