When you discuss the mechanics of breathing, which expression of Poiseuille's law do you use?

(Answer to Q. 1)  ANS: C
Poiseuille's law states that the pressure gradient required to cause a liquid to move through a tube is equal to the flow of the liquid through the tube multiplied by the resistance to flow. In a dis-cussion of gases, the term flow of the liquid is replaced with flow of the gas. Therefore, the flow of the gas is equal to the pressure gradient divided by the resistance to flow.

(Answer to Q. 2)  ANS: B
Poiseuille's law can be rewritten as: P = Q  (8nl)/(r4). According to this equation, the fol-lowing statements can be made. The more viscous a fluid, the greater the pressure gradient re-quired to cause it to move through a given tube. The resistance offered by a tube is directly pro-portional to its length. The pressure required to achieve a given flow through a tube must increase in direct proportion to the length of the tube. The resistance to flow is inversely proportional to the fourth power of the radius. Small changes in the radius of a tube will cause profound in-creases in the resistance to flow through that tube.

(Answer to Q. 3)  ANS: D
Bernoulli stated that As the forward velocity of a gas, or liquid, moving through a tube increas-es, the lateral wall pressure of the tube will decrease. Venturi postulated that pressure drops of fluids moving through constriction along a tube can be reversed if there is gradual dilation in the tube distal to the constriction. The Coanda effect is also based on the Bernoulli principle and demonstrates that water or gas flow can be deflected through a full 180 by careful placement of postconstriction extensions. Reynolds' number is the result of this mathematical equation: NR = v  d  (2r/). The turbulent flow is greater when the Reynolds' number exceeds 2000.

(Answer to Q. 4)  ANS: A
Transitional flow is a mixture of laminar and turbulent flows that typically occur where tubes di-vide. See Figure 1-15. Restricted flow occurs when narrowing or constrictions occur along the length of a tube. Laminar and turbulent flows can become restricted if an obstruction is encoun-tered along the length of a tube.

(Answer to Q. 5)  ANS: B
With turbulent flow, the movement of fluid molecules becomes chaotic and the orderly pattern of concentric layers seen with laminar flow is lost. Transitional flow is the mixture of laminar and turbulent flows. If the movement of fluid is said to be streamlined, it is laminar. Fluid mechanics does not describe the flow of fluids as being random.

(Answer to Q. 6)  ANS: A
Tubular is the only word in the list that does not describe a pattern of flow.