Ch. 4: Fluids

Question 1

Fluids

Answer 1

Substances that have the ability to flow and conform to the shape of their containers. Fluids can exert perpendicular forces, but cannot exert shear forces. Liquids and gases are the two phases of matter that are fluids

Question 2

Solids

Answer 2

Do not flow and they retain their shape regardless of their containers

Question 3

Density

Answer 3

Mass per unit volume of a substance (fluid or solid)

Question 4

Pressure

Answer 4

Defined as a measure of force per unit area; it is exerted by a fluid on the walls of its container and on objects placed in the fluids. A scalar quantity; its value has magnitude only, and no direction. The pressure exerted by a gas against the walls of its container will always be perpendicular (normal) to the container walls

Question 5

Absolute pressure

Answer 5

The sum of all pressures at a certain point within a fluid; it is equal to the pressure at the surface of the fluid (usually atmospheric pressure) plus the pressure due to the fluid itself.

Question 6

Gauge pressure

Answer 6

The name for the difference between absolute pressure and atmospheric pressure. In liquids, gauge pressure is caused by the weight of the liquid above the point of measurement

Question 7

Pascal’s Principle

Answer 7

States that a pressure applied to an incompressible fluid will be distributed undiminished throughout the entire volume of the fluid

Question 8

Archimedes’ principle

Answer 8

Governs buoyant force. When an object is placed in a fluid the fluid generates a buoyant force against the object that is equal to the weight of the fluid displaced by the object. Direction of the buoyant force is always opposite of gravity. If max buoyant force is larger than the force of gravity on the object, the object will float– this will be true if the object is less dense than the fluid it is in. If max buoyant force is smaller than the force of gravity on the object, the object will sink- true if object is more dense than fluid.

Question 9

Cohesion vs Adhesion

Answer 9

Fluids experience cohesive forces with each other, giving rise to surface tension. Fluids experience adhesive forces w other materials

Question 10

Viscosity

Answer 10

Measurement of a fluid’s internal friction

Question 11

Fluid Dynamics

Answer 11

A set of principles regarding actively flowing fluids

Question 12

Viscous drag

Answer 12

Nonconservative force generated by viscosity

Question 13

Inviscid

Answer 13

A property of ideal fluids, no viscosity

Question 14

Laminar flow

Answer 14

Fluids can move w either laminar flow (smooth and orderly– layers of fluid flow parallel to each other) Rate of laminar flow is determined by relationships in Poiseuille’s law– On MCAT, incompressible fluids are assumed to have laminar flow and v low viscosity while flowing, allowing us to assume conservation of energy

Question 15

Turbulent flow

Answer 15

turbulent flow (rough and disorderly). Causes the formation of eddies– swirls of fluid of varying sizes occurring typically on downstream side of an obstacle.

Question 16

Continuity Equation

Answer 16

Statement of the conservation of mass as applied to fluid dynamics

Question 17

Bernoulli’s equation

Answer 17

Expression of conservation of energy for a flowing fluid. This equation states that the sum of the static pressure and the dynamic pressure will be constant between any two points in a closed sys

Question 18

Venturi effect

Answer 18

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

Question 19

Circulatory system

Answer 19

Behaves as a closed system w nonconstant flow. Resistance decreases as total cross-sectional area increases: Arterial circulation is primarily motivated by the heart. Venous circulation has 3X the volume of arterial circulation and is motivated by the skeletal musculature and expansion of the heart. Inspiration and expiration create a pressure gradient not only for the respiratory sys, but for the circulatory system as well. Air at alveoli has essentially 0 speed.