Physics

Question 1

Atomic mass vs atomic number

Answer 1

Atomic mass is number of protons and neutrons in the nucleus

Atomic number is the number of protons in the nucleus of n atom

Question 2

What are isoptopes

Answer 2

Atoms of the same element have the same number of protons but different number of neutrons.

Question 3

Describe different types of chemical bonding

Answer 3

Covalent bonds: the negatively charged electrons are shared between atoms creating a bond with positive protons. Formed between non metallic compounds eg water

Iconic bond: an outer electron is transferred from one atom to another. The result is a more negative charged receiver atom (anion) and a positive charged atom that lost the electron (cation). This results in an electrostatic attraction

Dipole dimple interactions

Hydrogen bondings

Question 4

Define latent heat and give formula

Answer 4

Latent heat is the energy required to transform matter from one state to the other l. Latent heat of fusion is the energy required to change one unit of mass from solid to liquid. Latent heat of vaporisation is the energy required to change one unit of mass from liquid to gas.

Q = m • L

Q= energy required
m = mass
L = latent heat

Question 5

Wha is heat capacity. What is the formula ?

Answer 5

The specific heat capacity of a substance determines the energy needed to raise 1 kg of the substance by a temperature of 1 celsius.
unit: j g -1C-1

Q = c • m • 🔼T

Q= the energy required 
c = the specific heat capacity 
m = mass 
🔼T= temperature change

Question 6

Draw the graph showing the energy needed to produce change in state

Answer 6

draw

x axis: energy
y axis: temperature
important points: boiling and freezing points
the plateu at phase change
the different phases

Question 7

what is a phase diagram?
what is a triple point?
draw one for water

Answer 7

a phase diagram is graph that displays the relationship between solid, liquid and gaseous state of a substance as a function of temperature, volume and pressure
triple point: triple point is a combination of pressure and temperature where all three staes, solid, liquid and gas can co exist

for water:
x axis: temperature in celcius important points: 0.01 which is triple point, 374 which is critical temperature

y axis: pressure in bar. important points: 0.006 bar which is triple point, 218 bar which is critical pressure

Question 8

What is critical temperature ? What is critical pressure?

Answer 8

Critical temperature of a gas is the temperature at or above which no amount of pressure, however great will cause the gas to liquefy.
Critical pressure is the minimum pressure required to liquefy the gas a the critical temperature

Question 9

Give the critical temperature and pressure for the following substances:

Water
Nitrous oxide 
Carbon dioxide
Oxygen
Xenon

Answer 9

Substance Critical pressure bar critical temp C
H2O: 218 374
N2O: 72.7 36.5
CO2: 73 31.1
O2: 50 -119
Xe: 0.8 -112

Question 10

What do carbon - 14 and nitrogen - 14 have in common?

a: they have exactly the same atomic mass
b: the have exactly the same atomic number
c: they have approximately the same atomic number
d: they have approximately the same atomic mass
e: they are isotopes of carbon - 14

Answer 10

a: they have exactly the same atomic mass

Question 11

SBA:
A molecular liquid differed from a molecular gas because:
a: it has a higher density?
b: it has stronger intermolecular forces
c: it has stronger interatomic forces
d: it has a lower temperature
e: its molecules have less thermal motion

Answer 11

b: it has stronger intermolecular forces

Question 12

SBA:
Regarding plasma, which one of the following is true?
a: a plasma can exist in liquid or gaseous state
b: plasma forms at very low pressures
c: plasma forms at very high temperatures
d: an electric field is needed to form a plasma
e: plasma is highly stable

Answer 12

c: plasma forms at very high temperatures

Question 13

SBA:

20. 9 kJ of energy would raise the temperature of 1 kilogram of water at atmospheric pressure by
    a: 0.2 C
    b: 0.5 C
    c: 2 C
    d: 5 C
    e: 20 C

Answer 13

water has a specific heat capacity of 4.18jg-1C-1

d: 5C
20. 9/4.18 + 5

Question 14

MCQ:
Latent heat of fusion
a: is the amount of heat required to raise the temperature of water by 1C
b: is the amount of heat required to boil 1kg of water
c: is the amount of heat liberated when 1kg of steam freezes
d: is the amount of heat liberated when 1kg of steam condenses
e: is the amount of heat required to melt 1kg of ice

Answer 14

c and e

Question 15

Which of the following are vapours?

a: fog at 12 C
b: nitrogen at 375C
c: Nitrous Oxide at 25C
d: isoflurane at 50C
e: Invisible steam a the spout of kettle at 100C

Answer 15

c, d , e

Question 16

Which of the following are true of water?

a: it is a vapour at 100C on Mount Everest
b: increasing the pressure of liquid water can cause it to freeze
c: increasing the pressure of steam can cause it to condense
d: has a triple point temperature grater than 0C
e: can exist only as a gas or a solid in a vacuum

Answer 16

a, c, d, e

Question 17

Which of the following process liberate energy?

a: ionisation
b: condensation
c: freezing
d: melting
e: deposition

Answer 17

b, c, e

Question 18

Which of the following are true for any substance?

a: the gaseous state cannot edit at temperatures below the triple point
b: the liquid state cannot exist at pressure below triple point
c: the liquid state cannot exist at temperatures above the critical temperature
d: at 1 atmosphere of pressure all gases become liquids if cooled sufficiently
e: all liquids expand when they solidify

Answer 18

b, c

Question 19

What is force?

Answer 19

A force is an influence capable of producing a chance i the velocity of a mass

Question 20

What is velocity?

What is acceleration?

Answer 20

The velocity of an object refers to the speed and direction in which it moves.
Acceleration is the rate of change of velocity with respect to time. Acceleration can be change in either speed or direction or both.

Question 21

What is Newtons first law?
what is Newtons second law?
What is Newtons third Law?

Answer 21

1: Objects movie a straight line at constant speed, or remain stationary unless force acts upon the object
2: Acceleration of body is proportional to the force applied and inversely proportional to the mass of the object.
3: Every action of a force produces an equal and opposite reaction

Question 22

Formula for newtons second law:

Answer 22

F = m • a

F= force in N ( kg • m • s-2  )
m= mass of the object kg
a= acceleration of the object m • s-2 (meters per second squared)

Question 23

what is the formula to work out weight?

Answer 23

w = m • g

w = weight in N 
m = mass in kg 
g = acceleration due to gravity m • s-2

Question 24

What is pressure?

what is the formula for pressure?

Answer 24

The force applied to an object per unit surface area.
P = F/ A

P = pressure (pascal or N •  m -2 )
F= force in N 
A = are in m2

Question 25

What is Hooke’s law?

Answer 25

applied to a spring: there is a linear relationship between the force applied and the extension of a spring, within the elastic limits for that spring.

F = -k • x

F is the force applied
x is the extension
k is the spring constant

the spring constant is the degree of stiffness or springiness. The higher the spring constant the more difficult is it to extend.

Question 26

What is Viscosity

What is the difference between a newtonian fluid and a non newtonian fluid?

Answer 26

Viscosity is the measure of a fluids resistance to flow.
A Newtonian fluid has a accountant viscosity regardless of flow rate.
A non- Newtonian fluid has a viscosity that changes with flow rate.
Si unit for viscosity is pascal second or piseuille or poise.

Question 27

What is surface tension?

Answer 27

The result of the attraction between molecules across the surface of a liquid.

Question 28

What is Laplace’s equation for a cylinder?

Answer 28

🔺P = Tcyl/ R

T the total surface tension and the elastic wall tension
R vessel radius
🔺pressure difference between the inside and outside of the vessels

In other words the larger the radius of a vessel is the greater the wall tension required to withstand a given internal fluid pressure

Question 29

What is critical closing pressure?

Answer 29

The blood pressure at which a blood vessel suffers complete collapse and a halting of all blood flow . The reassure outside a vessel must exceed the intravascular pressure.

Question 30

What is the laplace’s equation for a spherical bubble?

How is it relevant in physiology?

Answer 30

🔼P = 2 • Tsph/ R

🔼P the pressure difference between the inside and outside
T sph the surface tension
R radius

Alveoli lines with fluid have a significant surface tension. This is highest when the alveoli are small.

Question 31

What is work done?
What is the formula ?
What is power?

Answer 31

Work done is the amount of energy applied by or to a system.

Woke done = F • d

F force
d distance the force has acted over.

Power is the rate at which work is done/ rate of transfer of energy.

Power= work done/ time taken

Question 32

What is energy?
What is the unit for energy?
What is the unit for power?

Answer 32

Energy is the capacity for doing work.

Unit of energy is the joule. One joule is the amount of energy required to exert a force of one newton through a distance of one meter.

The unit for power is watt, which is the equivalent of 1 J/s

Question 33

What is hysteresis?

Answer 33

A measurement differs according to whether the value is increasing or decreasing.

Question 34

What is compliance ?

What is formula?

Answer 34

The change of volume with respect to pressure. It is a measure of ease of expansion.

C = 🔼V / 🔼P

C compliance : m• N-1
V volume
P pressure

Question 35

What is elastance?

Answer 35

Elastance is the opposite of compliance and is the reciprocal value of of the compliance value.

Question 36

List three methods of heat transfer from one body to another

Answer 36

Conduction - flow of heat by conduction via direct collision between the atoms and molecules of warmer and cooler regions and the resultant transfer of kinetic energy.

Convection : the transfer of heat from a body by the liquid or gas which surrounds it.

Radiation

Question 37

List the thermometric properties of the following thermometers

Liquid in glass
Bimetallic strip
Bourdon
Resistance 
Thermister
Thermocouple 
Infrared

Answer 37

Liquid in glass- expansion of liquid 
Bimetallic strip- expansion of solid 
Bourdon - pressure change of gas
Resistance - resistance of coil of wire
Thermistor- resistance of metal oxides 
Thermocouple- seebeck effect 
Infrared- thermal radiation

Question 38

What is the Seebeck effect:

Answer 38

When a junction is formed between two dissimilar metals a small voltage is produced. This voltage varies with Temperature.

Question 39

What is the gay Lussack or third gas law?

Answer 39

Temperature is directly proportional to pressure of gas if volume is constant

Question 40

What is the combined gas law?

What is the universal gas law?

Answer 40

Combined gas law: p • V proportional T
So can be derived that
P1 • V1 / T1 = P2 • V2 = T2

Universal gas law:
P • V = nRT

Universal gas constant R is 8.31 J K-1 mol-1
N= number of moles

Question 41

What is Ficks law?

Answer 41

Rate of transfer of a gas through a membrane is proportional to the tissue area and the difference in gas partial pressure between two sides and inversely proportional to tissue thickness.

Question 42

Give the ficks diffusion equation:

Answer 42

V gas = D • A/T • ( P1-P2) 
 V = Rate if diffusion of gas 
D = diffusion constant
T= thickness to diffuse through
P1 P2 = partial reassure of gas on either side

Question 43

What does Graham’s law of diffusion say?

Answer 43

Graham’s law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of their density.

Question 44

What is the diffusion constant:

Answer 44

The diffusion constant allows for the diffusion rate of a particular gas through a membrane to be calculated and is worked out knowing the gases solubility and the molecular mass of the gas.

D = solubility of the gas / square root of molecular mass

Question 45

Give the thermometric properties of the following thermometers: 
liquid in glass
bimetallic strip
bourdon 
resistance
thermistor
thermocouple
infrared

Answer 45

liquid in glass: expansion of a liquid
bimetallic strip: expansion of solid
bourdon: pressure change of gas 
resistance: resistance of coil of wire
thermistor: resistance of metal oxides
thermocouple: Seebeck effect 
infrared: thermal radiation

Question 46

Discribe how Resistance, thermistor and thermocouple thermometers work.
What are their advantages and disadvantages.

Answer 46

Resistance: resistance of coil of wire ( e.g platinum wire) measured and converted into temperature using a calibration equation. Advantage is that is cheap and simple. Linear relationship with temperature, however not as sensitive as a thermistor.

Thermistor: Temperature sensitive resistor ( resistance changes with Temperature). Uses mostly semiconductor (metal oxides) whose resistance increases with a fall in temperature. i.e. they have negative thermal conductivity. Disadvantage is that they have a non- linear resistance versus temperature characteristic, however can be corrected by using appropriate calibration equation. they are cheap, small and easy to use. they are very accurate. often placed into pharynx, oesophagus, rectum or bladder.

Thermocouple: Seebeck effect ( When a junction is formed between two dissimilar metals a small voltage is produced across the junction. This voltage varies with temperature. ) Small, accurate if correctly calibrated and respond rapidly. Can be used to measure temperature o very small volumes of matter.

Question 47

What is frequency?

What is the relationship between frequency and wavelength?

Answer 47

Waves are a series of repeating disturbances that propogate in space and time. Frequency is the number of oscillations that occurr per second and are expressed as cylces per second or watt.

Ther is an inverse relationship between frequncy and wavelength. The higher the frequency, the shorter the wavelength.

Question 48

What is the doppler effect?

Answer 48

An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other.

Question 49

What is atmospheric pressure in atm, kpa, cmH2O?

Answer 49

1 atmospheric pressure = 1 atm = 101.3 kPa = 1033cmH2O = 760mmHg

Question 50

Give the following in values of kPa:

mmHg 
atm
bar
milibar
cmH2O
psi

Answer 50

1 mmHg = 0.1333kPa
1 atm = 101.2 kPa
1 bar = 100 kPa
1 milibar = 0.1 kPa
1 cmH2O = 0.0907 kPa
1psi = 6.895 kPa

Question 51

Give three ways of measuring pressure:

Answer 51

manometer, bourdon gauge, barometer

manometer: compares the pressure of two gases one being a reference pressure and the other being the sample pressure. The simples design would be a U-shaped tube of glass partially filled with a liquid. The columns change in height in direct proportion to the pressure difference between the sample and the reference pressure. Often simple manometers have the reference tube open to atmosphere.

The bourdon gauge: This measures gauge pressure. The C shaped hollow spring like tube extends outwards at the sealed end when the pressure within it rises. It gives a comparison of the pressure within the tube to the pressure outside. ( uses Boyle’s law i.e. with increased pressure the volume of a gas will also rise) The expansion/ contraction of the tube is relayed to a pointer that indicates the pressure on a calibrated dial.

The barometer: a special type of manometer for measurement of atmospheric pressure. An inverted glass tubing filled with liquid ( e.g mercury) onto a bath of same fluid. The atmosphere will push onto the bath of fluid until the height of the fluid i.e the pressure exerted by the column of fluid is the same as the pressure exerted by atmosphere.

Question 52

What causes over and under damping of the arterial blood pressure waveform?

Answer 52

underdamping: oscillation of the sensor diaphragm appears as high- frequency waves superimposed on the pressure signal. causes over estimation of systolic and diastolic blood pressure.
overdamping: the sensor response is sluggish leading to under estimation of systolic pressure and over estimation of diastolic pressure. occurs of catheter is too long or too thin. An air bubble in the catheter can also lead to dramatic increase in damping.

Question 53

What is Saturated Vapour Pressure?

Answer 53

The Saturated Vapour pressure of a liquid is the maximum pressure exerted by the evaporated molecules above the liquid at equilibrium. The higher the temperature, the greater the vapour pressure.

Question 54

What is the dew point?

Answer 54

The temperature at which water vapour condenses to liquid is called the dew point.

Question 55

What is absolute and relative humidity?

Answer 55

Absolute humidity is the mass of water molecules present per unit volume air. Expressed as grams per cubic meter.
Relative humidity is the percentage of actual humidity relative to the maximum humidity possible (the saturation point ) at a given temperature.

relative humidity = (actual vapour density/ saturation vapour density) x 100%

Question 56

What is a device measuring humidity called?

Give different ways of measuring humidity:

Answer 56

Hygrometers measure humidity.
Devices:
1. Wet and dry bulb hygrometer:
A dry thermometer measures ambient temperature. A wet thermometer is surrounded by a wet wick. As the system equilibrates the temperature in the wet thermometer will drop due the the latent heat of vaporisation. The degree of temperature drop in relation to the ambient temperature can be used to work out relative humidity using a psychometric chart.
2. Hair tension hygrometers:
Hair lengthens in a consistent fashion when water is added. A hair under tension and exposed to the environment can be calibrated to give reading of relative humidity.
3. Regnault’s hygrometer: silver tube containing ether. As air is bubbled through the ether it vaporises cooling the tube. The temperature at which the surrounding air condenses around the tube is the dew point. If the ambient temperature and the saturated vapour pressure at that point are known then the relative humidity can be calculated using a psychrometric chart.

Question 57

What is the mass of water in a fully saturated air at sea level at 20 degrees Celsius and 37 degrees Celsius?

What is the partial pressure of water when fully saturated at body temperature?

Answer 57

at 20 C fully saturated absolute humidity at seal level is 17 g/m3.
at 37 C fully saturated absolute humidity at sea level is 44 g/m3
Partial pressure of water at 37 degrees is approximately 6kPa

Question 58

How does the heat and moisture exchange filter work? What are its advantages and disadvantages?

Answer 58

HMEF filters are a sealed unit at the patients end which contains hygroscopic material e.g silica gel or calcium chloride. When pt breaths out the warm moist air hits the filter and water condenses onto filter. The filter warms due to latent heat of condensation. When cold air is inhaled this process is reversed. Addition of a 0.2 micrometer filter renters the interface impermeable to bacteria and viruses. 
Its cheap (disposable), passive and efficient for up to 24 hours. It is about 80% effective. 
It is passive, adds dead space onto circuit and also adds resistance. Filter can get clogged up with secretions.

Question 59

What is the hagen- poiseuille law?

what is the formula to calculate flow?

Answer 59

Hagen- Poiseuille law calculates resistance of a tube for a given fluids. It assumes that the liquid is incompressible, viscous and that flow is laminar.

Q = (π x r4 x 🔼P) / 8 μL

Q = flow (has a dot at the top usually to state rate of flow)
 r= radius
P = pressure
μ = viscosity
L= Lenght

flow is directly proportional to the fourth power of radius and inversely proportional to length.

Question 60

What is Reynolds number?

Answer 60

Reynolds number allows us to predict whether flow is going to be turbulent or laminar.

Re = (2 x r x v x p) / μ

Re = Reynolds number
r = tube radius
v= velocity
p = fluid density
μ = viscosity

Flow is laminar if Reynolds number is less 2000. If Reynolds number is over 4000 flow is turbulent. In between these two numbers the flow is transitional.

Question 61

What is the relationship between flow and pressure for turbulent flow?

Answer 61

The rate of flow is proportional to the square root of pressure. The graph of pressure versus flow in turbulent flow is an exponential line compared to the laminar flow where the line is straight. In laminar flow flow is directly proportional to pressure.

Question 62

How do the following flow meters work? 
variable orifice flow meter
rotating - vane flowmeter
pneumotachometer
wright peak flow meter
benedict - roth spiromenter

Answer 62

variable orifice flow meter: an accurate needle valve is attadhed to a variable orifice flute with a bobbin inside. As the needle valve is opened the flow of fresh gas causes the bobbin to move upwards until the force acted on by gravity is equal to the force acted by flow. As the tube gets wider at the top than at the bottom the only thing that affects the position of the pin is flow rate.

Rotating - vane flowmeter: the sensor has a small turbine in the low path which rotates in relation to flow. A light source is passed through the sensor which is interrupted by the turning turbine. The interruption in light sensed is converted to voltage which is proportional to flow.

Pneumotachometer: a circular tube with a wire mesh is attached to the flow tube. The wire mesh causes resistance to flow. Two pressure transducers are attached to either side of the mesh. The calculated pressure difference between the two transducers i proportional to flow according to ohms law.

Wright peak flow meter: Low cost device, which can measure peak flow. A diaphragm is attached to a spring which opposes its movement. Blowing into the device will move the diaphragm agains the spring until the spring forces overcome air pressure. A sliding marker is attached to the diaphragm and will move with the diaphragm to indicate flow.

Benedict roth spirometer: This is an expandable compartment consisting of counterbalanced bells. This compartment will increase in volume with pressure. A wire attached to the top of the bell is attached to a maker writing on a rotating paper. As the patient breathes in and out the bells will expand and collapse causing the marker to go up and down on the paper producing a flow recording. ( now this is sensed and recorded electronically)