WEEK 7 (Hydrostatics)

Question 1

Describe the molecules in Solids, Liquids & Gases

Answer 1

SOLIDS = molecules are rigidly bound resulting in a definite shape and volume

LIQUIDS = molecules are not bound together with a definite force to maintain a definite shape

GAS = molecules are not bound together therefore has neither a definite shape or volume - gases completely fill the vessel in which it is contained

Question 2

What are three different categories that are difficult to categorise into solid, liquid or gas

Answer 2

• Gels
• Colloids
• Filamentous molecules form liquid crystals

Question 3

Define Gels

Answer 3

Cross-linked networks of polymer molecules

Question 4

Define Colloids

Answer 4

Suspensions of macromolecules or microscopic particles

Question 5

Describe the Ideal fluid

Answer 5

• No viscosity (no frictional resistance to flow)
• Incompressible (doesn’t change volume)

Question 6

How do you calculate density?

Answer 6

mass/volume

Question 7

How do you calculate Pressure?

Answer 7

force/area

Question 8

Describe the movement of fluid molecules in rest

Answer 8

There is no net force but molecules still move due to thermal motion or diffusion

Question 9

Why does the pressure in fluid increase with depth?

Answer 9

Due to the weight of fluid above

P2 - P1 = pgh (to calculate fluid pressure)
P - density
g - gravity
h - height

Question 10

What is Pascal’s principle?

Answer 10

Pressure applied to any part of a liquid is transmitted undiminished to other parts of liquid

Question 11

What is Archimede’s principle?

Answer 11

A body submerged in a fluid partially or wholly is buoyed upwards by a force that is equal in magnitude to the weight of displaced fluid

F = pgV
P - density
g - gravity
V - volume

Question 12

What are the two types of fluid motion?

Answer 12

Laminar (streamline) flow & Turbulent flow

Question 13

What are the clinical applications of fluid motion?

Answer 13

Both laminar and turbulent flow of blood are important

• Heart valves need turbulent flow to operate
• Turbulent flow from jagged wounds help to form clots more rapidly, it shears blood platelets and releases protein to form clots
• Turbulent flow allows measuring of blood pressure

Question 14

What is the correlation between turbulent blood flow and blood pressure measurement?

Answer 14

When the turbulent flow sound APPEARS the SYSTOLIC is measured. When the turbulent flow sound DISAPPEARS the DIASTOLIC is measured.

Question 15

What does Bernoulli’s equation state?

Answer 15

Within a horizontal flow of fluid, points of higher fluid speed will have less pressure than points of slower fluid speed.

Question 16

what is the application of Bernoulli’s equation in a blood vessel with an aneurysm?

Answer 16

As area increases, velocity decreases & pressure increases, the aneurysm becomes extremely dangerous

Question 17

what is the application of Bernoulli’s equation in a blood vessel with partial blockage due to atherosclerosis?

Answer 17

As area decreases, velocity increases & pressure decreases, surrounding tissue pressure may collapse the artery and cause stroke or heart failure

Question 18

What are the different components on Bernoulli’s equation?

Answer 18

p - pressure in the fluid
P - density
V - velocity of flow
A - area of cross-section

Question 19

What is the capillary effect?

Answer 19

the process of a liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces like gravity.