Lecture 2: Fluids

Question 1

What is a fluid?

Answer 1

A material that has the ability to flow

Question 2

Does a fluid have to be a liquid?

Answer 2

No, both liquids and gases are considered fluids

Question 3

What causes fluids to flow?

Answer 3

Basic forces like gravity or pressure

Question 4

Fluids and containers

Answer 4

Fluids assume the shape of their containers, unlike solids, which retain their shape

Question 5

What is hydrostatics?

Answer 5

The study of fluids that are NOT moving

Question 6

What are two important properties of hydrostatics?

Answer 6

Density and pressure

Question 7

What is hydrodynamics

Answer 7

The study of fluids in motion

Question 8

Pressure =

Answer 8

Force/area

Question 9

How do you increase pressure?

Answer 9

Increase force or decrease area

Question 10

How do you decrease pressure?

Answer 10

Decrease force or increase area

Question 11

At the same depth in a fluid, fluid exerts ___ pressure in all directions

Answer 11

The same

Question 12

What is Pascal’s principle?

Answer 12

The pressure applied to a confined fluid increases the pressure throughout the fluid by the same amount

Example: If you increase the pressure on a contained fluid by 5 psi, the pressure everywhere in the fluid goes up by 5 psi

Question 13

If you’re applying a pressure of 3 psi on the plunger of a syringe with a plugged needle, how does the pressure in the barrel compare to the pressure in the needle?

Answer 13

Pressure is equal throughout (Pascal’s principle)

Question 14

What is Archimedes Principle?

Answer 14

An object immersed either totally or partially in a fluid feels a buoyant force equal to the weight of the fluid displaced

Question 15

If the density of an object is greater than the density of the fluid, then the object will ___

Answer 15

Sink

Question 16

If the density of the object is less than the density of the fluid, then the object will ___

Answer 16

Float

Question 17

If the object sinks, the buoyant force is ___

Answer 17

LESS than the true weight of the object

Question 18

If the object floats, the buoyant force is ___

Answer 18

GREATER than the true weight of the object

Question 19

What is a hydrometer?

Answer 19

A device used to measure the specific gravity of liquids

Question 20

What are two types of flow?

Answer 20

• Laminar

- Turbulent

Question 21

What is laminar flow?

Answer 21

Unchanging flow pattern, smooth and orderly

Question 22

What is turbulent flow?

Answer 22

Continuously varying pattern of flow, abruptly changing and chaotic

Question 23

In anesthesia, we strive for…

Answer 23

LAMINAR flow

Question 24

What is flow rate?

Answer 24

The volume of fluid passing a particular point per unit time (i.e.: 3L/min)

Question 25

Narrowing causes speed to...

Answer 25

Increase tremendously

Question 26

Narrowing causes flow rate to...

Answer 26

Remain the same

Question 27

Fluid flows at a ___ speed through the narrow part of the tube

Answer 27

Greater

Question 28

What is Bernoulli’s Principle?

Answer 28

As the speed of a fluid increases, the pressure exerted by the fluid decreases

Question 29

What was discovered by the Venturi tube flowmeter?

Answer 29

The pressure is lower in the narrow part of the tube; basis of a nebulizer treatment

Question 30

What is viscosity?

Answer 30

A measure of a fluid’s resistance to flow

Question 31

Fluids with high viscosity flow...

Answer 31

Do not flow very readily (i.e.: honey)

Question 32

Fluids with low viscosity flow...

Answer 32

Flow more easily (i.e.: water)

Question 33

The closer a molecule is to a wall...the ___ it moves

Answer 33

Slower

Question 34

What is Poiseuille’s Law?

Answer 34

The laminar flow rate of an incompressible fluid is proportional to the fourth power of the radius of the tube it is flowing through

Question 35

Poiseuille’s equation applies to...

Answer 35

Laminar flow only

Question 36

What are 3 factors that flow type depends upon?

Answer 36

- Speed - Density - Viscosity

Question 37

What are 3 possible ways to increase the fluid flow rate through a catheter or needle (according to Poiseuille’s Law)?

Answer 37

1. Raise IV bag height or add a pressure bag to IV bag 2. Use a larger gauge IV catheter 3. Use a shorter length catheter

Question 38

What is Reynold’s number?

Answer 38

Reynold’s number is a dimensionless quantity that is used to characterize fluid flow; it is the measure of the tendency for turbulence to occur

Question 39

When Reynold’s number rises above 2000, what happens?

Answer 39

Turbulence will usually occur, even in a straight, smooth vessel

Question 40

Reynold’s number is proportional to what 3 quantities?

Answer 40

- Density - Velocity - Tube diameter

Question 41

Reynold’s number is inversely proportional to...?

Answer 41

Viscosity