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BMAT > 🅱eet > Flashcards

🅱eet Flashcards

1
Q

acceleration=?

A

change in velocity/time

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2
Q

what is the difference between speed and velocity?

A

that velocity is the speed with a direction:

speed is a scalar quantity – it is the magnitude of the velocity. velocity is a vector quantity; it is direction-aware.

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3
Q

momentum=?

A

mass x velocity

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4
Q

force=?

A

mass x acceleration

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5
Q

what is newton’s first law?

A

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

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6
Q

what is inertia?

A

the natural tendency of objects to resist changes in their state of motion, sometimes newtons 1st law is called the law of inertia.

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7
Q

what is conservation of momentum?

A

a fundamental law of physics which states that the momentum of a system is constant if there are no external forces acting on the system. It is embodied in Newton’s first law (the law of inertia).

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8
Q

what is momentum?

A

the quantity of motion of a moving body, measured as a product of its mass and velocity.

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9
Q

what is rate of change of momentum equal to?

A

resultant force

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10
Q

what is the difference between mass and weight?

A

mass-measure of the amount of matter an object is made up of. No matter where you are at given moment in time, mass is constant. measured in g and kg.
weight-a variable and a vector. its direction of pull is towards the centre of the planet. tis measured in Newtons.

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11
Q

what equation links mass and weight?

A

w=mg.
w=weight in newtons
m=mass in kg
g=gravitational field strength in N/kg

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12
Q

what is the gravitational field strength on earth approximated as?

A

10 N/kg

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13
Q

what is newtons third law?

A

For every action, there is an equal and opposite reaction.

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14
Q

what is the law of conservation of energy?

A

the total energy of an isolated system remains constant, energy can neither be created nor destroyed, it can only be transformed or transferred from one form to another.

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15
Q

what are some types of energy?

A 
magnetic
kinetic
thermal
radiant (light)
GPE
sound (energy coming from a vibrating object)
chemical
electrical
elastic potential (stored energy in stretch or squashed objects)
nuclear (stored in the nuclei of atoms)
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16
Q

what is happens to wasted energy?

A

it is transferred to its surroundings and spreads out so much that it becomes difficult to do anything useful with it.

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17
Q

what is useful energy?

A

The portion of final energy which is actually available after final conversion to the consumer for the respective use.

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18
Q

percentage efficiency=?

A

(useful output/total output)x 100

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19
Q

density=?

A

mass/volume

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20
Q

what does a wave do?

A

transfers energy without the net movement of matter.

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21
Q

what are some examples of longitudinal waves?

A

sound waves
ultrasound waves
seismic P-waves

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22
Q

what happens in longitudinal waves?

A

the vibrations are parallel to the direction of wave travel. show areas of compression and rarefaction: compressions are regions of high pressure due to particles being close together,rarefactions are regions of low pressure due to particles being spread further apart.

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23
Q

what are some examples of transverse waves?

A

electromagnetic waves – eg light waves, microwaves, radio waves
seismic S-waves
ripples on the surface of water

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24
Q

what happens in transverse waves?

A

the vibrations are at right angles to the direction of wave travel, peaks and troughs.

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25
Q

what is amplitude?

A

the maximum extent of a vibration or oscillation, measured from the position of equilibrium.

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26
Q

what is wavelength?

A

the distance between successive crests of a wave.

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27
Q

what is frequency?

A

the number of crests of a wave that move past a given point in a given unit of time. The most common unit of frequency is the hertz (Hz), corresponding to no of crests per second.

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28
Q

what is period?

A

the time needed for one complete cycle of vibration to pass in a given point.

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29
Q

what equation links frequency and period?

A

frequency= 1/period

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30
Q

what does 1Hz mean?

A

1 wave per second

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31
Q

wave speed (m/s)=?

A

frequency (Hz) x wavelength (m)

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32
Q

what is the nature and properties of electromagnetic waves?

A

transverse

travel at the speed of light through a vacuum.

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33
Q

what are the uses of ultrasound?

A

sonar, scanning, animals

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34
Q

what are the parts of the spectrum (in order)?

A 
radio
microwave
infrared
visible light
UV
x-rays
gamma
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35
Q

what are the wavelength, frequency, and energy levels like at the gamma part of the spectrum?

A

shorter wavelength
higher frequency
higher energy

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36
Q

what are the wavelength, frequency, and energy levels like at the radio part of the spectrum?

A

longer wavelength
lower frequency
lower energy

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37
Q

what is the wavelength of gamma rays ?

A

< 0.01 nanometers

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38
Q

what is the wavelength of radio waves like?

A

longer than 1 mm.

39
Q

uses of radio waves?

A

communication such as broadcasting television and radio, communications and satellite transmissions.

40
Q

uses of microwaves?

A

cooking food, communications and for satellite communications

41
Q

uses of IR?

A

electrical heaters, cookers for cooking food, short-range communications like remote controls, optical fibres, security systems and thermal imaging cameras.

42
Q

uses of visible light?

A

photography and illumination,fibre optic communications

43
Q

uses of gamma rays?

A

sterilising food and medical instruments, and in the treatment and detection of cancer.

44
Q

uses of x rays?

A

scanning the internal structure of objects and in airport security scanners, internal imaging.

45
Q

uses of uv?

A

sterilise surgical equipment, sterilise food, produce vitamin D, check bank note forgeries, disinfecting water.

46
Q

dangers of uv?

A

can cause the skin to burn,can cause damage to skin cells and eyes, and increase the risk of skin cancer and cataracts. ionising radiation.

47
Q

dangers of gamma and x rays?

A

ionisation can cause the mutation of genes, which can lead to cancer.

48
Q

dangers of microwaves?

A

Intense sources of microwaves can be dangerous through internal heating of body cells.

49
Q

dangers of IR?

A

The heating effect of IR can cause burns to the skin.

50
Q

what was thomsons model of the atom?

A

plum pudding model:
atoms are spheres of positive charge
electrons are dotted around inside.

51
Q

what was rutherfords model of the atom?

A

atoms have a central positively charged nucleus where most of the mass is, electron orbit the nucleus-planetary model.

52
Q

what did bohr add to the atomic model?

A

the fact that electrons occupy energy levels around the nucleus.

53
Q

what is radioactive decay?

A

the process by which an unstable atomic nucleus loses energy through radiation

54
Q

what are alpha particles?

A

2 protons and 2 neutrons, same as a helium-2 nucleus.

55
Q

what happens when a nucleus loses an alpha particle?

A

mass number -4

atomic number -2

56
Q

what are beta particles?

A

high speed electrons

57
Q

what happens when a nucleus loses a beta particle?

A

atomic no +1

no change to mass number

58
Q

what happens when a nucleus loses gamma?

A

no change, gamma is only energy

59
Q

what is random nature of radioactive decay?

A

you can’t know precisely when it will next happen, there’s no pattern.

60
Q

what is the spontaneous nature of radioactive decay?

A

it happens on its own. You don’t need any external forces to get the isotope to decay.

61
Q

what is the activity of a radioactive sample?

A

the average number of disintegrations per second.

62
Q

what is the unit of activity of a radioactive sample?

A

the becquerel (Bq).

63
Q

how do you calculate acitivity of a radioactive sample?

A

ΔN/ Δt (change in number of undecayed nuclei/change in time in seconds)

64
Q

what is the decay constant?

A

the probability that a nucleus will decay per second,so its unit is s-1.

65
Q

how do you find activity using the decay constant?

A

activity = decay constant x the number of undecayed nuclei

66
Q

what is the 🅱enetrating 🅱ower of alpha?

A

skin/ paper

67
Q

what is the 🅱enetrating 🅱ower of beta?

A

3 mm aluminium foil

68
Q

what is the 🅱enetrating 🅱ower of gamma?

A

Lead/concrete

69
Q

how ionising is alpha?

A

high

70
Q

how ionising is beta?

A

low

71
Q

how ionising is gamma?

A

v low

72
Q

what are the sources of background radiation?

A

Cosmic rays – radiation that reaches the Earth from space
Rocks and soil – some rocks are radioactive and give off radioactive radon gas
Living things – plants absorb radioactive materials from the soil and these pass up the food chain
radioactive waste from nuclear power stations, radioactive fallout from nuclear weapons testing and medical x-rays.

73
Q

what is background radiation?

A

a measure of the ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.

74
Q

what is half life?

A

the time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve.

75
Q

what is nuclear fission?

A

nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei).

76
Q

what is nuclear fission caused by?

A

absorption of neutrons

77
Q

what is nuclear fusion?

A

a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.

78
Q

what are the steps of fusion and what kind of reaction is it?

A

1H (proton)-2H (deuterium) - 3He - 4He

proton-proton chain

79
Q

why does fusion need such a high temperature?

A

high temperature gives the hydrogen atoms enough energy to overcome the electrical repulsion between the protons.

80
Q

what are the dangers of using electrostatics?

A

It is dangerous when there are flammable gases or a high concentration of oxygen. A spark could ignite the gases and cause an explosion.
It is dangerous when you touch something with a large electric charge on it. The charge will flow through your body causing an electric shock. This could cause burns or even stop your heart. A person could die from an electric shock.

81
Q

what charge does polythene become?

A

negative

82
Q

what is the unit for charge?

A

coulombs (C)

83
Q

what is the charge of 1 electron?`

A

1.6 x 10^-19 C

84
Q

how do we make it easier to talk about charge?

A

electron has -1e of charge and proton has 1e of charge where e is 1.6 x 10^-19.

85
Q

current=?

A

charge/time

86
Q

what is resistance?

A

ratio of potential difference to current.

87
Q

resistance=?

A

voltage/current

88
Q

what is power?

A

energy transferred per second.

89
Q

power=?

A

current x voltage

90
Q

when does electromagnetic induction occur?

A

when a wire moves relative to a magnet or when a magnetic field changes.

91
Q

what is a generator?

A

a coil of wire revolving in a magnetic field.

92
Q

what is work?

A

the transfer of energy from 1 store to another.

93
Q

what is a field?

A

an area of space in which a force is felt.

BMAT (4 decks)

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