Physics Flashcards

1
Q

Laminar flow

A

The situation when any fluid (gas or liquid) passes smoothly and steadily along a given path, as described by the Hagen Poiseuille equation

Viscosity is the important property for laminar flow

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2
Q

Turbulent flow

A

When a fluid flows unpredictably with multiple eddy currents, and is not parallel to the sides of the tube through which it flows

Density is the important property for turbulent flow

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3
Q

Reynold’s Number

A

A dimensionless number which describes the likelihood of fluid flow being either turbulent laminar.
<2000 likely to be laminar
>2000 likely to be turbulent

Re = pvd/n

P is densitv
V is velocity
D is diameter of tube
N is viscosity

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4
Q

Hagen-Poiseuille equation

A

Flow = pi p r4 / 8 nl

P is pressure drop
R is radius
N is viscosity
L is length

Flow is proportional to the 4th power of the radius so if r doubles then flow increases x 16

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5
Q

Bernoulli Principle

A

An increase in flow velocity of an ideal fluid will be accompanied by a decrease in pressure in order to conserve energy

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6
Q

Venturi Effect

A

The introduction of a constriction to fluid flow within a tube causes velocity to increase and therefore pressure to fall

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7
Q

Surgical diathermy

A

Works on the principle of current density, that a current applied over a small area has high density and heating will occur

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8
Q

Ultrasound

A

Sound waves with a frequency >20KHz

Medical ultrasound uses waves in the 2-15MHz spectrum

Increasing frequency gives greater resolution but reduces penetrating capacity

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9
Q

Piezoelectric effect

A

Phenomenon by which a mechanical stress applies to crystalline substances produces a potential difference

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10
Q

Resolution

A

Ability to distinguish to objects as separate

Can be spatial or contrast (those with similar echo reflective properties)

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11
Q

Power

A

The rate at which work is done, measured in watts

W=J/s where J is work done and s is time in seconds

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12
Q

Absolute Humidity

A

The total mass of water vapour present in the air per unit volume (AH, kg.m-3 or g.m-3 )

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13
Q

Relative Humidity

A

The ratio of the vapour pressure of water in the air compared with the saturated vapour pressure of water at that temperature (RH, measured as a %).

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14
Q

Dew Point

A

The temperature at which the relative humidity of the air exceeds 100% and water condense out of the vapour phase to form a liquid.

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15
Q

Humidity

A

The amount of water vapour present in the atmosphere and is subdivided into two types: absolute and relative

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16
Q

Latent Heat

A

The heat required or released when a substance changes state

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17
Q

Heat Capacity

A

The heat energy required to raise the temperature of a given object by one degree

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18
Q

Specific Heat Capacity

c = ΔQ/mΔT

A

the amount of heat energy required to raise the temperature of a mass of 1kg by 1 Kelvin.

c = ΔQ/mΔT
where…
• c = the specific heat capacity of the substance
• ΔQ = the amount of heat energy required in kilojoules (kJ)
• m = the mass of the substance being heated in kilograms (kg)
• ΔT = the change in temperature in Kelvin (K)

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19
Q

The Triple Point of Water

A

The temperature at which all three phases of water are in equilibrium at 611.73Pa. It occurs at 0.01oC.

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20
Q

Force

A

Force is that influence which tends to change the state of motion of an object, measured in Newtons

F = ma m=mass and a=acceleration

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21
Q

Newton

A

1 Newton is that force which will give a mass of 1Kg an acceleration of 1m/s/s

N = Kg.m.s-2

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22
Q

Pressure

A

Pressure is force applied over a unit area, measured in pascals

P=F/A

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23
Q

Pascal

A

1 Pascal is equal to a force of one newton applied over an area of one square metre (N.m-2)

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24
Q

Energy

A

Energy is the capacity to do work, measured in joules. (mechanical, chemical, electrical or thermal/heat)

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25
Q

Work

A

Work is the result of a force acting upon an object to cause its displacement in the direction of force applied

J=FD where F is force and D is distanced travelled.

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26
Q

Joule

A

1 Joule is the work done when a force of one newton moves one metre in the direction of the force.

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27
Q

Power

A

Power is the rate at which work is done, measured in watts

W=J/s where J is work done and s is time in seconds

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28
Q

Watt

A

1 Watt is the power expended when one joule of energy is consumed in one second.

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29
Q

Critical Temperature

A

The temperature above which a gas cannot be liquified regardless of how much pressure is applied

30
Q

Critical Pressure

A

The pressure needed to liquify a gas at its critical temperature

31
Q

Boyle’s Law

A

At a constant temperature, the volume of a fixed amount of a perfect gas varies inversely with its pressure

32
Q

Charles’ Law

A

At a constant pressure, the volume of a fixed amount of a perfect gas varies in proportion to its absolute temperature

33
Q

Gay-Lussac’s Law

A

At a constant volume, the pressure of a fixed amount of a perfect gas varies in proportion to its absolute temperature

34
Q

Gas vs Vapour

A

A gas is above its critical temperature
A vapour is a substance in the gaseous phase below its critical temperature - and can be liquified with increased pressure

35
Q

Henry’s Law

A

The amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid

36
Q

Dalton’s Law

A

In a mixture of gases, the pressure each gas exerts is the same as if it existed alone in the same volume

37
Q

Avogadro’s constant

A

Equal molar volumes of all gases under standard temperature and pressure occupy the same volume

38
Q

A mole
6.02x10^23

A

The quantity of a substance that contains the same number of molecules as there are atoms as there are in 0.12g of Carbon 12

39
Q

Viscosity

A

A liquid’s resistance to flow (Pascal-seconds)

40
Q

Density

A

Mass of a substance per unit volume (g/mL)

41
Q

Osmole

A

The number of particles equal to Avogadro’s number - 6.02 x 10^23

42
Q

Osmolarity

A

The number of osmotically active particles per LITRE of SOLUTION
(mmols/L)

43
Q

Osmolality

A

The number of osmotically active particles per KILOGRAM of SOLVENT
(mmols/Kg)

44
Q

Osmotic Pressure

A

The pressure exerted within a sealed system of solution in response to the presence of osmotically active particles on one side of a semi-permeable membrane
(kPa)

45
Q

Colligative Properties

A

Those properties of a solution that vary according to osmolarity:
Depression of freezing point
Reduction of vapour pressure
Elevation of boiling point
Increase in osmotic pressure

46
Q

Raoult’s law

A

Depressing of freezing point/reduction in vapour pressure of a solvent is proportional to the molar concentration of the solute

47
Q

Surface tension

A

The IMF developed at the surface of a liquid that tends to resist the action of external forces (N.m-1)

48
Q

LaPlace’s Law
(sphere)

A

T=Pr/2 (T is wall tension, P is pressure, r is radius)

A given wall tension, a sphere of smaller radius will have greater pressure, hence why a balloon is difficult to inflate at first/small alveoli collapse without surfactant

49
Q

Resistance

A

Opposition to flow of direct current (ohms)

50
Q

Reactance

A

Opposition to flow of alternating current (ohms)

51
Q

Impedance

A

Total of the resistive and reactive components of opposition

52
Q

Ohm’s Law

A

At a constant temperature

V=IR

V is voltage, I is current and R is resistance

53
Q

Capacitor

A

A device that stores electrical charge

54
Q

Capacitance

A

The ability of a capacitor to store charge (farads, F)

55
Q

Farad

A

A capacitor with a capacitance of one farad will store one coulomb of charge when one volt is applied

F= C/V

56
Q

Inductor

A

An electrical component that oppose changes in current flow by the generation of an electromotive force

57
Q

Inductance

A

The measure of the ability to generate EMF under the influence of changing current (henry, H)

58
Q

Henry

A

One henry is the inductance when one ampere flowing in the coil generates a magnetic field strength of one weber

H=Wb/A

59
Q

Wheatstone Bridge

A

An electrical circuit designed to measure an unknown resistance, by balancing two limbs of a bridge circuit so the voltage between the limbs is zero

R2/R1 = Rx/R3

60
Q

Resonance

A

The condition in which an object or system is subjected to an oscillating force having a frequency close to its own natural frequency

61
Q

Natural Frequency

A

The frequency of oscillation that an object or system will adopt freely when set in motion or supplied with energy (hertz, H)

62
Q

Damping

A

A decrease in the amplitude of an oscillation as a result of energy loss from a system owing to frictional or other resistive forces

63
Q

Semi-conductor

A

Materials with conductivity between conductors and insulators.
Reasonably well bound outer shell electrons but with additional energy, the electrons are able to move and allow current to flow.

64
Q

Cleaning

A

The process of physically removing foreign material from an object without necessarily destroying any infective material.

65
Q

Disinfection

A

The process of rendering an object free from all pathogenic organisms, EXCEPT bacterial spores.

66
Q

Sterilisation

A

The process of rendering an object free from all pathogenic organisms, INC bacterial spores.

67
Q

Decontamination

A

A combination of cleaning, plus disinfection or sterilisation.

68
Q

Under-damped

A

Output value oscillates around the baseline for some time
Coefficient = 0-0.3

69
Q

Over-damped

A

Overly blunted, inaccurate
Coefficient > 1

70
Q

Zero Damping

A

Theoretical situation (vacuum)
Coefficient = 0
Amplitude of oscillations does not diminish with time

71
Q

Critical Damping

A

No overshoot, so very accurate but too slow
Coefficient = 1

72
Q

Optimal Damping

A