Flashcards in Physics Quiz #4 Deck (59)
Both liquids and gases are fluids?
What are the forces associated with fluids(3)?
What is friction?
-the resistance to flow from the surface interaction
-it is proportional to viscosity
What is viscosity?
The inherent property of a fluid that resists flow
What is the result of pressure forces in a fluid established by differences in pressure from one point to another, which creates a pressure gradient?
-all flow moves from higher pressure, or resistance to lower
What is Laminar flow?
a type of flow which all molecules of a fluid travel in a parallel path within the tube
Which molecules in laminar flow encounter the least adhesive force of the walls of the tube?
molecules in the center of the tube
Molecules in the center of the tube move at a velocity twice that of the mean flow?
True laminar flow predominates in the smallest airways(terminal bronchioles)?
What is transitional flow?
a mixture of laminar flow along the walls of the tube with turbulent flow in the center
What is turbulent flow?
described as chaotic with irregular eddies throughout
Which law is described: In straight circular tubes, the radius will have the most dramatic effect on flow = constancy X Radius to the 4th power(r^4) X pressure gradient
According to Poiseuille's law, doubling the radius will result in_____-fold increase in flow; tripling of the radius increases the flow by_____-fold?
Resistance is inversely proportional to r^4(the greater the radius, the smaller the resistance).
When the radius of a tube is tripled, how much will the resistance decrease?
Resistance is directly proportional to fluid viscosity(the greater the blood viscosity, the greater the resistance).
Resistance is directly proportional to tube length(the longer the tube, the greater the resistance).
How are flow and resistance related?
-flow through a tube is inversely proportional to resistance
-if resistance doubles, flow is halved
-if resistance is halved, flow is doubled
Whose law is described: When considering flow through a tube, the gradient in hydrostatic pressure(inflow pressure minus outflow pressure) equal flow times resistance.
Whose law is described: MAP-CVP = CO x SVR or SVR = (MAP-CVP)/CO x 80
What happens to flow and what happens to resistance when the radius of the tube increases? When radius of the tube decreases?
-When the radius of a tube increases, resistance to flow decreases and flow increases
-When the radius of a tube decreases, resistance to flow increases and flow decreases
Is flow through 16 gauge IV catheter greater or lesser than through a 20 gauge catheter?
-the greater the radius, the more flow
What happens to fluid flow if viscosity is increased?
Patients with polycythemia have ___ blood flow due to ___ viscosity of blood. Patients with anemia have ___ blood viscosity, hence ___ flows through tissues.
Polycythemia = decreased, greater
Anemia = decreased, greater
How will flow be affected when length of a tube increases? If the length of tube is decreased by 50%? If the length of a tube is doubled?
-flow will decrease
-flow will double
-flow will be decreased by half
If the radius of a tube decreases to 1/3 of its original size, flow will decrease to 1/81 of its original value?
Which of the following will decrease peak inspiratory pressure? 1. change ETT from 8.0 to 6.0 or 2. change ETT from 6.0 to 8.0?
changing ETT from a 6.0 to a 8.0 will decrease the PIP, PIP is greater when inflow resistance is higher and vice versa
These interventions are a direct manipulation of whose law: To improve flow when delivering a unit of PRBC's a large-diameter IV catheter is recommend, a pressure bag may be placed on the unit of PRBCs to increase the driving pressure(pressure gradient) and the PRBCs may be diluted with normal saline to lower viscosity.
Which factor will have the most dramatic improvement on flow: increasing the pressure, thinning the liquid(less viscous), shortening the tube, or increasing the diameter of the IV catheter?
increasing the diameter of the catheter