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# MCRT Sciences

### Physics sect 1, 2, 3

Question | Answer |
---|---|

Define Work. | The product of the force exerted on an object and the distance the object is moved. |

Express the formula calculating Work. | W = F x d |

Define Power. | The rate at which work is done. |

Write the formula used for calculating Power. | P = W / t |

Define Energy | The ability to do work. |

List the two form of mechanical energy. | kinetic energy potential energy |

Define Mass. | The quantity of matter contained in an object. |

Define Acceleration. | The rate of change in velocity. |

Define Velocity. | A measure of linear distance over time. |

Define Force. | A vector that produces or prevents motion. The product of mass times acceleration., |

Write the formula for kinetic energy. | Ke = 1/2 mv^2 |

Write the formula for potential energy. | Kp = mgh |

Define potential energy. | The energy of an object due to its position or configuation. |

Define velocity | Measure of a linear distance over time. |

Define flow | A volume of liquid moving across a given point over time. Unit volume per unit time. |

For a constant flow system, what happens to the velocity of the flowing fluid when it encounters a decrease in the total cross sectional area? | The velocity increases. |

For a constant flow system, what happens to the velocity of the flowing fluid when it encounters a increase in the total cross sectional area? | The velocity decreases. |

What is the product of the cross-sectional area and the velocity? | flow |

Describe what happens to the diameter and length of each airway generation proceeding in the direction from the trachea to the alveoli. | The diameter decreases and the length decreases. |

Distinguish between irregular and regular dichotomous airway branching. | Regular branching forms symmetrical daughters, Irregular the daughter branches differ from the parent in both length and diameter. |

What is the approximate total cross-sectional area of the alveoli? | 70 square meters or 700,000 square centimeters. |

Describe the activity at the alveolar level of the gas molecules of an inspired volume. | Gas moves through diffusion. |

Explain why the velocity of blood flow in the pulmonary artery decreases as the blood enters the pulmonary capillaries. | Because the cross sectional area in the pulmonary capillaries is larger. |

Describe the Bernoulli principle. | The relationship between lateral wall pressure (LWP) and velocity for an incompressible fluid flowing through a tube in laminar or streamline fashion. That relationship is inverse. |

Upon what physical law is the Bernoulli principle based? | The law of conservation of energy. |

Discuss the relationship between lateral wall pressure and the fluid velocity as described by Bernoulli. | As velocity increases, LWP decreases. |

Relate the interaction between lateral wall pressure and fluid velocity to a flowing fluid encountering a partial obstruction. | The velocity must increase, therefore the LWP decreases. |

Draw and label a diagram of the conduction system depicting the Bernoulli principle. | see pg 357 |

What happens to the lateral wall pressure gradient when the density of the gas flowing across the partial obstruction is increased? | If the density of the gas increases the LWP will decrease further. |

What is the rationale for helium-oxygen therapy in patients with airway obstruction? | Heli-ox is 6 times less dense than room air. So, the LWP is increased. |

Draw and label an air-entrainment system. | see pg 363 |

List the two flow components that comprise an air:O2 ratio. | The flow of the entrained gas and the flow of the source gas. |

List the air:O2 rations for an FiO2 of (a) 0.60 (b) 0.40 (c) 0.24 | (a) 1:1 (b) 3:1 (c) 25:1 |

Define viscosity. | A fluids resistance to deformity. |

What is the difference in airway resistance between laminar and turbulent flow? | resistance associated with laminar flow in substantially less. |

Describe the influence cardiac oscillations purportedly have on gas diffusion in lung regions so affected. | the oscillations enhances gas exchange. |

Define conventional ventilation. | Ve = f x Vt |

Describe the three components of the total resistance to ventilation. | Inertial- get the gas moving Elastic- move (stretch) the lung tissue Raw- radius of the airway |

What is the essential prerequisite for a fluid to flow? | pressure gradient |

How does airway resistance differ across the tracheobronchial tree. | large airways contribute 90% of the resistance and the small airway contribute 10% |

What are the two factors that contribute to airway resistance? | pressure gradient and flow or radius of the airway and length of the airway |

Why is early small airway disease hard to detect? | Small airways contribute a significantly smaller resistance than larger airways. |

Write Poiseuille's law and describe each of the factors comprising it. | see pg 390 |

Rewrite Poiseuille's law and show how it can be used to illustrate the relationship among 'P', 'V', and r^4 | ∆P / flow = η8L / πr^4 |

If all other factors in Poiseuille's law remained constant except radius and airway resistance, what would be the effect on the airway resistance if the radius (a) doubled and (b) decreased by half? | (a) Raw would decrease by 16 fold (b) Raw would increase by 16 fold |

Created by:
smiddleton