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# MCAT Physics Ch 4

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

Fluids | Substances that have the ability to flow and conform to the shape of their containers. They exert perpendicular forces, but cannot withstand shear forces. Two of its phases of matter include liquids and gases. |

Solids | Substances that do not flow and retain their shape regardless of their containers. |

Density | mass per unit volume of a substance (fluid or solid) |

Pressure | force per unit area, which is exerted by a fluid on the walls of its container and on objects placed in the fluid. It is a scalar quanitiy with mag. only, and no direction. |

Note About Pressure Exerted By A Gas In A Container | The pressure exerted by a gas against the walls of its container will always be perpendicular to the container's walls. |

Absolute Pressure | Sum of all pressures at a certain point within a fluid, which is equal to the pressure at the surface of the fluid (atm. presure) + pressure of the fluid itself. |

Gauge Pressure | Difference between absolute pressure and atm. pressure. |

Note About Gauge Pressure In Liquids | Gauge pressure in liquids is caused by the weight of the liquid above the point of measurement. |

Pascal's Principle | An applied pressure to an incompressible fluid will be distributed throughout the entire volume of a fluid. |

Hydraulic Machines | Machines that operate based on the application of Pascal's principle to generate mechanical advantage. |

Archimedes' Principle | When an object is placed in a fluid, the fluid generated a buoyant force against the object that is equal to the weight of the fluid displaced by the object. |

Note About Direction Of Buoyant Force In Arch. Princ. | Direction of buoyant force is ALWAYS opposite to direction of gravity. |

Note If Max. Buoyant Force > Grav. Force | If max. buoyant force is larger than grav. force on the object, the object will float. This will be true even if the object is less dense than the fluid it is in. |

Note If Max. Buoyant Force < Grav. Force | If max. buoyant force is smaller than grav. force on the object, the object will sink. This will be true even if the object is more dense than the fluid it is in. |

Note About Fluids And Cohesive Forces | Fluids experience cohesive forces with molecules of the same fluid |

Note About Fluids And Adhesive Forces | Fluids experience adhesive forces with other materials |

Cohesive Forces | These are forces that result in surface tension |

Fluid Dynamics | A set of principles that regard actively flowing fluids |

Viscosity | Measurement of a fluid's internal friction. |

Viscous Drag | Non-conservative force generated by viscosity |

Laminar Flow | Flow of liquids that is based on the relationships in the Poiseuille's law |

Note About Incompressible Fluids | They are assumed to have laminar flow and low viscosity when flowing to assume conservation of energy. |

Continuity Equation | Statement of conservation of mass as applied to fluid dynamics. |

Bernoulli's Equation | Expression of conservation of energy for a flowing fluid. The sum of the static pressure and dynamic pressure will be constant between any two points in a closed system. |

Venturi Effect | For a horizontal flow, there is an inverse relationship between pressure and speed. In a closed system, there is a direct relationship between cross-sectional area and pressure exerted on the walls of the tube. |

Note About The Circulatory System | The circulatory system behaves as a closed system with nonconstant flow |

Note About Cross-Sectional Area | Resistance decreases as the total cross-sectional area increases. |

Note About Arterial Circulation | It is primarily motivated by the heart. |

Note About Venous Circulation | It has 3X the volume of arterial circulation, and is motivated by the skeletal musculature and expansion of the heart. |

Note About Inspiration / Expiration With Pressure Grad. | They create a pressure gradient for the respiratory system, and the circulatory system. |

Note About Air At The Alveoli | It has essentially zero speed. |

Eq. 4.1: Density Equation | d = m / v |

Eq. 4.2: Weight Of A Volume Of Fluid | Fg = dvg |

Eq. 4.3: Specific Gravity | SG = d / 1g/cm^3 |

Eq. 4.4: Pressure | P = F/A |

Eq. 4.5: Absolute Pressure | P = Po + pgz. P0 = incident / ambient pressure. z = depth of the object. |

Eq. 4.6: Gauge Pressure | Pgauge = P - Patm = (p0 + pgz) - Patm |

Eq. 4.7: Pascal's Principle | P = F1/A1 = F2/A2. F2 = F1(A2/A1). A1/A2 = Cross sectional area |

Eq. 4.8: Buoyant Force | Fbuoy = dfluid * Vfluiddisplaced * g = dfluid * vsubmerged * g |

Eq. 4.9: Poiseuille's Law | Q = pi*r^4 * Del. P / 8*nL. n (eta) = viscosity of fluid, L = length of pipe. |

Eq. 4.10: Critical Speed | Vc = Ng*n / dD. n(eta) = viscosity of fluid, Ng = Reynold's number. |

Eq. 4.11: Continuity Equation | Q = v1A1 = v2A2 |

Eq. 4.12 Bernoulli's Equation | P1 + 1/2 dv1^2 + dgh1 = P2 + 1/2 dv2^2 + dgh2 |

Created by:
SamB91