3-12;Pressure/Flow/Pumps/Surface Tension

Question 1

states of matter

Answer 1

solid=internal order and fixed atomic positions
liquids=takes shape of container, no rigidity, atoms have very strong cohesive forces that hold them together
gas=only forces exerted are due to collisions

Question 2

ideal fluid

Answer 2

fluid is non-viscous=internal friction is negligible) and incompressible (density is constant)

Question 3

pressure

Answer 3

exertion of force upon a surface by an object/fluid

force/area [N/m^2 or Pa]

Question 4

what does the penetrating ability of an object depend on

Answer 4

depends on pressure, not only force since a sharper needle will require less force to produce required penetrating pressure

Question 5

pressure in liquids

Answer 5

at rest pressure caused by liquid is proportional to depth of liquid density

Question 6

how is pressure exerted in a static liquid

Answer 6

liquid pressure is exerted equally in all directions so that net force is 0

Question 7

pascal’s principle

Answer 7

any change of pressure in an enclosed fluid is transmitted undiminished to all parts of the fluid

Question 8

clinical applications of pascal’s principle

Answer 8

chronically ill patients develop decubitus ulcers/bedsores, mainly on elbows due to exertion of largest pressure = prevented by use of water mattress = P evenly distributed against every part of body in contact w/ mattress

cerebrospinal fluid = increase in P = increases P in all part of fluid so if there is a tumour, will cause an increase in P

unborn fetus protected by amniotic sac fluid = distributes forces exerted on abdominal area equally = mother cautioned against tight clothes

Eye contains enclosed fluid = blow to front of eye transmits P to backof eye = Optic nerve/retina/blood vessels injured by XS P

Question 9

buoyancy

Answer 9

when something is being immersed in fluid appears to be lighter than it does in air

Question 10

why is buoyancy needed

Answer 10

to provide lifting force required to float a ship on water or balloon in air

Question 11

how does buoyant forces arise

Answer 11

due to difference in liquid pressure above and below object

Question 12

Archimedes’ principle

Answer 12

buoyant force on submerged object = to weight of fluid displaced

he found objects weigh less under water: weight of object in air - weight when submerged = weight of water displaced = use this to determine vol of irregular shaped object and weight density by weight/vol

Question 13

what does pressure in flowing liquid depend on

Answer 13

depends on details of flow process, uniform pressure drop due to smooth flow through uniform tube

Question 14

why are there drops in pressure during flow

Answer 14

loss in energy due to frictional effects

Question 15

laminar flow

Answer 15

average flow speed that is 1/2 max speed found at centre, represents min energy loss

Question 16

turbulent flow

Answer 16

when flow speeds up past a certain critical speed or an obstruction in flow path to form eddies = causes laminar flow to break down into turbulent flow

Question 17

viscosity

Answer 17

frictional forces that oppose flow w/i fluid

Question 18

function of a pump

Answer 18

to increase pressure in a fluid to allow fluid to move in a desired manner to overcome system resistance

Question 19

types of pumps

Answer 19

lift or force pump

lift=lifts liquid rather than forcing it through system, completely mechanical, relies of Patm

force=don’t rely on Patm directly, circulates liquid in a sealed closed liquid circuit

Question 20

heart as a pump

Answer 20

the action of ventricles is a force pump, achieves XS P by contraction

Heart is 2 synchronous force pumps.

receives blood from Venous system and raises P to push it out into arterial system.

When RV expands, AV valve opens, lets venous blood flow into ventricle whilst SL valve remains closed to prevent backflow of previously pumped blood.

Question 21

what causes faults in pumping action of heart

Answer 21

valves that have holes or don’t close properly.

if R AV Valve isn’t closed, RV contraction pumps blood back out into venous system

if SL V isn’t closed = blood backflows from Arterial system when ventricle expands

Question 22

describe pressure in circulatory system

Answer 22

P highest when it leaves LV, lowest when enters RA.

P raised by RV to drop enter LA as low residual pressure

LV main pump = supplies P for systematic circulation through body

Question 23

why is P drop greater or lesser in arterioles than across capillaries

Answer 23

P drop depends on Vol Flow rate and resistance, since there are more capillaries than arterioles = vol flow rate through each capillary is much smaller

Question 24

why is it important to control vol flow rate of heart

Answer 24

to supply required oxygen and nutrients to cells

to reduce R of CS to enable body to respond to greater demands for blood during exercise w/o overburdening heart pump

EG. Moderate EX=increase blood flow rate^3 but BP only increases by small % = total R drops less than 1/2

Vigorous EX = larger fraction of blood flows to muscles = vasodilation of muscle tissue

Question 25

how is VFR controlled

Answer 25

blood pressure and internal radii used for short term control of VFR.

arterioles are surrounded by muscle cells so provide large changes in vessel diameters = known as resistance vessels

Question 26

applicability of Poiseuille’s law

Answer 26

departures from the law expected in capillaries due to distortion of RBC needed to fit through by 1/2 or smaller

law only applies to laminar flow but during exercise, turbulence may occur in aorta, this increases R = increase in P to increase VFR

Question 27

what are changes in blood speed during circulation

Answer 27

speed MAX in aorta, drops to MIN in capillaries then accelerates to high speed in major veins leading to heart

speed in capillaries is very large compared to aorta due to reduced diameter, but total area is order of 1000 larger than aorta so flow in caps assumed to be slowed by factor of 1000

Question 28

laplace law

Answer 28

showed wall tension is required to withstand a given fluid P proportional to vessel radius

so smaller vessel can withstand more pressure w/ a given wall strength, but if artery wall expands = too weak to provide required tension = so expansion places an even greater tension on membrane = classic vicious cycle

Question 29

what happens when blood flows to feet and upwards, what does this mean

Answer 29

gravitational potential energy reduced, some converted into P and Ke to aid heart

upward= some P and Ke used to overcome gravity = increases Gravitational Potential energy

so BP at head is lower when standing than lying on floor

Question 30

systolic pressure

Answer 30

peak pressure produced by ventricular contraction

Question 31

diastolic pressure

Answer 31

min pressure maintained by elastic system

Question 32

how is arteries adapted for contraction

Answer 32

arteries are comprised of extremely elastic system of tubing = so blood bulges out of walls leaving aorta to store energy as Elastic Potential energy = elastic expansion of wall travels along arteries like a wave = pulse

Question 33

where is P variation typical in

Answer 33

the arterial system only, it diminishes at arterioles and venous system

Question 34

absolute P

Answer 34

sum of atmospheric pressure and liquid pressure

Question 35

hydrostatic pressure

Answer 35

P exerted by fluid at rest due to force of gravity

EG when u dive to bottom of swimming pool

Question 36

hydrometer

Answer 36

measures specific gravity of liquid

glass tube of standard specific gravity floating in liquid

if specific gravity increases = hydrometer floats

EG urinometer

Question 37

specific gravity

Answer 37

ratio of density of substance to density of some substance, usually pure water

Question 38

urinometer

Answer 38

measures specific gravity of urine to identify disease, which alters composition of urine = changes its specific gravity